[Lenovo ZUK Z2 (Plus) Guides, News, & Discussion] n'wah:
Alright, so after ROM-hopping for quite a bit over the past three months, I've got a fairly good idea about the various ROMs for our device, unofficial or otherwise. With Oreo coming out soon, and most Nougat ROMs getting their final builds, I thought this might be a good time to give my impressions. While old-timers might not get much use out of this, I'm hoping this will help out anyone that's recently bought a Z2, or is new to XDA.

INTRODUCTION

So, you got a Z2 and are looking to try a new custom ROM to get away from the horror show that is ZUI. Well, I've got good and bad news for ya.

The good- well, if you're a "normal" user that uses his phone to call, text, browse and game for a bit, most ROMs are gonna please you. Most of them are "stable" at this point, meaning you'll get very few crashes/random restarts unless you go full ham installing esoteric Xposed modules. But if you're new to XDA, you're probably unaware of Xposed anyway.

The bad- Most of them will also have some minor issues, and the only way to know if a ROM is perfect for you is to try it. Everyone has their own use cases/expectations from a ROM and thus will have a different experience than you.

My usage: I do not use Google Apps, except for Maps. Most of the apps I use are free/open source, except a few unavoidable one's like banking apps and WhatsApp. That being said, I've tried most(all?) of these ROMs with both Gapps and no Gapps to get a fair impression. Played a few games too, to test the phone in demanding situtations.

I have divided this guide into categories, roughly based on a users requirements. You can't have your cake and eat it too. Usually, if a ROM has insane performance, battery life tends to suffer. The key, as with all things in life, is finding the right balance. When a category has numerical ratings, I will be using a relative scale out of 10. A 10 does not mean that a ROM is perfect in an area, only that it was the best one that I came across.

With that lengthy, but neccessary introduction out of the way, here's the guide:

CATEGORY A: I want my phone to fly, battery life be damned!

I feel that 3 ROMs fit the bill here:

1. VIperOS by [MENTION=5964093]jneto3000[/MENTION]

2. Citrus CAF by [MENTION=8078618]DD3Boh[/MENTION]

3. Pure Fusion OS by [MENTION=6540928]devabhi[/MENTION]

While Viper has been the smoothest by a tiny margin, all these ROMs have amazing performance, and ran anything I threw at them without a hitch. I never had any UI lags while scrolling in apps. That being said, each does have a drawback. With Viper, I've always had a bit of a delay in the fingerprint scanner, PureFusion has been (slightly) unstable for me, and Citrus CAF hasn't recieved the latest KRACK patches, which makes it a no-go from a security POV.

Overall Ratings:

ROM RATING

Viper 10

Citrus CAF 9.5

PureFusion 9.5

Jaguar 9

LineageOS 8.8

crDroid 8.3

AquariOS 8

CarbonROM 7.8

NOTE: Just because I said, "Battery life be damned", doesn't mean all these ROMs have atrocious battery life. In fact, I got ~6.5 hrs SOT with Citrus CAF + Gapps, which is pretty good.

CATEGORY B: I want a good mix of performance, stability and battery life.

I'm guessing most of you belong to this category. Well you're in luck, because most ROMs for Z2 also belong to this category. You can have your pick amongst:

1. LineageOS by [MENTION=5719417]varotone[/MENTION]. Was personally my favorite ROM, extremely stable, lightning fast fingerprint, good performance (lagged a bit in games, but butter smooth for other apps) and good battery life. Unfortunately, it hasn't, and will probably never recieve patches for the KRACK vulnerability, so the more security conscious amongst you might want to avoid it. EDIT: Turns out, we did a get a new build, with the same great performance+battery life, but it does have a slow fingerprint unlock, when the phone has been asleep for a while.

2. Jaguar by [MENTION=5075064]optimumpro[/MENTION]. Similar to Lineage, it had frame drops with Games, but was rather smooth otherwise. I used this before Lineage, but my screen-on-time reduced drastically after a couple of weeks :(. On the flipside, many users have, and continue to report good battery life with it, so take my words with a grain of salt. r17 really improves the GPS performance.

3. crDroid by [MENTION=6623671]Subhrajyoti Sen[/MENTION]. Insane battery life. I got ~8.5 hrs of SOT (without Gapps) on my second charge cycle. Began to lag a bit so I switched to Viper, although the latest unofficial build has rectified the performance issues. Haven't tried it myself though.

4. AquariOS by [MENTION=7395699]kenny3fcb[/MENTION]. Nothing much to say, just a stable ROM with a good battery life. Hasn't been updated for quite sometime though, so no KRACK or Blueborne vulnerability patches.

CATEGORY C: I want security and longevity

Security conscious? Want frequent updates?

The answer, lads- is Jaguar by [MENTION=5075064]optimumpro[/MENTION], and honestly- it's not even close. I think the only way to find the best ROM for yourself is to find a dev whose priorities/use cases align with yours. And if security is your priority- then [MENTION=5075064]optimumpro[/MENTION] is your man.

Damn, I sound like a sales guy.

On a serious note though, while I have little idea what Jaguar's security features like- "hardened bionic" do from a technical standpoint, I can tell you that it's usually the first ROM to incorporate security patches and tweaks, from Google or other sources. The dev takes out the time to respond to most queries, and he's said that the ROM will be maintained and updated till Oreo gets completely stabilized.

It has come to my attention that the dev apparently does not release the source code for Jaguar, so I can no longer recommend Jaguar as a privacy-focused ROM.

CATEGORY D: I want a great battery life

1. crDroid by [MENTION=6623671]Subhrajyoti Sen[/MENTION]. The last official build gave me the best overall battery life I've had yet.

2. CarbonROM by [MENTION=4924861]ankit99[/MENTION]. Pretty good idle consumption. My battery dropped just 1% overnight. Unfortunately not very stable, and hasn't been updated in a while.

Other noteworthy ROMs

1. AEX by [MENTION=2823824]davidevinavil[/MENTION]. While I personally didn't a have a great experience with v4.6 of this ROM, a lot of people have. And the dev has always been active, answering most queries. It's worth trying out the 22nd July build, which is pretty good, but doesn't have any recent security patches.

2.. AEX Unofficial by [MENTION=7030080]Star_king12[/MENTION]. While ROM has been discontinued, the dev was very helpful with user queries. Also, the 13th September build gave me some of the best battery life I've had on the Z2. I think he's working on a new ROM, so keep an eye out!

I haven't tried every ROM for the Z2, and I'm sure there are few good ones I've missed. Feel free to point to out any in the comments.

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I'm personally using the last ViperOS build for now, and will continue to do so, if the fingerprint issue doesn't bother me too much. If it does, I might give the latest PureFusion or (unofficial) crDroid builds a try. But by and large, I'm happy with Viper.

I hope this helps some of you.