[Samsung Galaxy S7 Questions and Answers] Tekkpriest:
Sorry for the late reply, work called.

Usually a BTU won't draw more battery or anything, since frequencies mostly are standard in every country. It's more like saved APN's etc. (which you can change manually via your phone's settings menu anyways). But as previously mentioned to the original poster, you can depending on where you live, loose out on VoLTE and Wifi-Calling, since those a carrier specific and usually not included in an unbranded ROM. If those are important to you, you probably want to stick with your current ROM, even if i do understand that new things are always fun. Even i did not wait for my carrier.. :D

But having OTA updates and stuff like that is convenient, otherwise you'd have to flash every update like this one, which is why i recommend using a full BTU firmware, if you really wanna do it. Well, you don't have to flash it manually.. but it won't change since OTA updates are CSC based. So for example if Android 7.1 or another security patch will come out, you will need to wait until your XEO (Poland, i presume?) firmware get's the corresponding update, which according to you might take ages, since the original Nougat is not even out yet.

If you only have an AP file, i recommend using updato.com / samfirmware to download the current image of the BTU. Since you will need Bootloader and Modem files aswell (BL, CP respectively), aswell as the CSC file. I have checked though, your current CSC is included in the OXA (multipurpose CSC) of the BTU. So you might wanna flash a non BTU image first to change the CSC to something not included in the BTU one. Otherwise you will need root access to change it manually and this triggers Knox as we all know and thus your warranty is gone. And if you flash a non BTU image, be sure to factory reset / clear cache via recovery mode after installing and then let it boot normally, so the CSC change will take effect, afterwards flash the BTU image will all files and do the same. Be sure to backup your data beforehand, since they will get lost and do NOT use the HOME_CSC file. This one is for not changing the CSC at all and will retain your data. Use the ROM's CSC. Also always check the rom for your model, i have seen people who used a 935F (which is the edge) ROM on a flat S7 (which is 930F in europe mostly). But that's why i highlight it. :)

If you have further questions, i'll answer them to the best of my abilities :)

Oh and i almost forgot, you don't need a pit file . It's really just for more engineerical purposes as explained in ODIN. Current Marshmallow and Nougat Roms consist of 4 parts, which include the corresponding PIT.

I highly recommend not using the PIT file, if you don't know what it entails (you will need to look on the internet for it, since it will be quite lengthy if i explain). In short, as long as an update does not use a different partition layout and / or you mess up your partitions by yourself, you just don't need it. And doing afromentioned, would require extensive knowledge about Android anyways. As long as you don't root and modify your system yourself, you most likely will always be fine. And since rooting does have it's drawback (like some Apps not working due to security, Samsung warranty void etc), i'd not recommend it anyways, unless you are experienced :)