As far as how tied to Disney they are: the project lead and initial sole developer (others chip in quite a bit now) is an employee of Disney. My impression is that he's open to changing things but not if those changes interfere or complicate their deployment at Disney. So I'd say definitely Disney-prioritized rather than a straight up community project. Affiliated projects like AutoPkg are community driven and somewhat tool agnostic.

I think what you should use depends on your available time, inclination and mindset. I meant for this to be short but it ended up being ridiculously long. Sorry about that. Hopefully it helps save you and anyone else the time required to get a broad understanding of this space. tl;dr at the bottom.

I wouldn't bother with Server App. It's complete crap. Maybe useful for >10 macs but I'm honestly not sure if that's even true given all the ways it can totally shit the bed on you. Not well maintained. Probably best to think of it more as a reference implementation for 3rd parties developing an MDM solution.

If you have time for the learning curve, want to apply the configuration as code/automated testing mindset and want/need to save money go with the open source tools. Don't expect to be able to commit the commercial versions to source control.
Munki+Reposado+Margarita+AutoPkg for sure:

Munki: Nothing touches it terms of the core/engine's package installation abilities. Repo is configured by the admin/tools like autopkg so it's just a static repo that can be hosted by any web server. Customizable self-service app that's very similar to the app store app.

Reposado: Let's you do pipeline/canary testing/one-some-many deployments of your official Apple updates since they can rarely mess things up on their own but more frequently break some software.

Margarita: Web UI for managing Reposado, only needed if you want/need that or just don't want to deal with figuring out how to manage/automate it.

AutoPkg: This is so amazing you'll want this even if you use something like Casper but it was designed with Munki in mind. Using recipes it downloads updates for software from the vendor's websites/repositories, repackages as necessary and can be configured to automatically add those as updates for your existing packages. So you can get security updates and force their installation long before your average laptop user bothers to update. You can do pipeline/canary testing/one-some-many deployments using your preferred CICD tool (Jenkins seems to be popular for this). Recipes are maintained in a community repo so even if a vendor changes their site and breaks things someone has probably noticed before you and provided a fix.

Key differentiators for these: Open Source, configuration management as code, automation, testing, CICD, etc.

Puppet, Chef, Ansible, Salt or GitHub's Boxen (Uses Puppet but has an opinionated layer on top): If you want more configuration management and distributing it via packages through Munki isn't your cup of tea use one of these in addition to Munki.
Key differentiators: Open Source, configuration management as code, automation, testing, CICD, etc.

If you want easy as pie and very SMB oriented take a look at JAMF's Bushel. It's clean looking and subscription based and probably the least amount of effort overall. It's cloud-only I believe, so if on-prem is a requirement look at the next one. Not sure if you can do custom packages or much in the way of config but you can definitely distribute Apple App store applications.
Key differentiators: modern, easy to use and quick to get started with. Auto-magic enrollment of devices you buy (as long as they are through the same account). Distributed App Store apps.

If you want more control and a decent GUI (particularly if you have a decent number of Macs) take a look at JAMF's Casper. Warning: The trial is limited to 14 days but you can purchase a 45 or 60 day trial+2 or 3 days of training for a mere ~$4K or $6K. Training I think is provided by a VAR/Partner. No you can't use it after that unless you buy it. Expect a hard and high touch sales experience since this is more or less enterprise software. There's a cloud version and on-prem version. On-prem will require some upkeep (MySQL instance to manage, java app that runs on tomcat, etc.). You should use AutoPkg with Casper too even if it's a bit annoying to get setup.
Key differentiators: Big community with a lot of answers and advice that are often universal enough to be useful no matter what you're using. Very enterprise-y so good if you need that (contract, support, feel good sales pitch to management). Easy to use for junior admins or support people. Easy self-service that customizable per-person/group. Auto-magic enrollment of devices you buy (as long as they are through the same account).

Note: The JAMF sales people might bring in a rep from Apple's Enterprise Support team during the sales process to talk about the benefits of Casper (they use it at Apple) as well as (surprise) pitch their enterprise support services and a package called enterprise connect. Enterprise connect is essentially a workaround for bad UX/bugs in Apple's directory services support that they want you to pay for. When the Apple rep told us that you'd be silly to use open source tools we asked about Google and Facebook and he replied, "Yeah... well they probably think they're pretty smart! Haha." Backpedaling ensued and he said, "Well of course they're smart, they just have different problems." When pressed about the problems Casper couldn't resolve for them he said "scale" after conferring with another person at Apple.

There are others but either I don't know enough about them to offer any insight or they aren't worth mentioning for various reasons.

tl;dr:

Munki/Reposado/AutoPkg: If you can afford the learning curve and need/want the DevOps tools/automation/philosophy.

Bushel: If you want easy, no hassle and automatic device enrollment, SMB.

Casper: If you want a GUI, enterprise features and automatic device enrollment, easy self-service, have a decent number of Macs.