Wow... from any point you approach ports, it ends up to become always overwhelming... ?
Don't let poudriere be thought of as overwhelming. It is not required, nor is a dedicated machine for that matter, but it will make porting effort more accurate, reliable, and easier. Its not too bad to setup and doesn't require a webserver+browser to read through its log output. It is nice in that it allows you to know your build environment is a clean build environment. If dependencies fail you get feedback, if files aren't in plist properly you get feedback, if library dependencies are missed you get feedback, etc. Once the setup is done you can sit back and say, 'build it again' and wait while 'poudriere go burr'. You may not have to do a cleanup between each and every little change when testing or want to inspect things which makes poudriere's test feature come in handy. I've been known to just break a step in a port to get poudriere test to stop me at the desired stage.
The reason for using CURRENT for multiversion testing is poudriere more reliably builds for the same and older FreeBSD versions than it builds for newer ones. So from current you could tell poudriere to go do a build for 13 and 14 to make sure they both build (again happens with each in its own clean environment and own logs as poudriere go burr). I usually run STABLE and an updated STABLE is always newer than the equivalent release branch so poudriere should be able to test for both (minus any bugs) but may be more likely to have some issues testing the even newer CURRENT. If you go with any one version, you may have a time where as maintainer you get contacted by users, committers, automated report tools, etc. about a problem observed with your port on or off of that system; if you plan ahead of time how to run other version tests then you can more quickly analyze and respond to the issue. If overwhelmed or you don't have access you can always ask others for help, logs, etc.
RELEASEs need to work if possible, STABLE is a heads up for upcoming issues that need to be fixed in your port and/or FreeBSD and CURRENT again is a heads up but wtih more drastic and frequent changes. "If" a port requires STABLE or CURRENT but doesn't work on release then the world doesn't end, but the port should set BROKEN accordingly and even if older systems aren't fixed to work having the port will help for future systems. If it breaks on newer stuff and its known, please also set BROKEN until it can be resolved.
With ZFS and boot environments you could have one of each FreeBSD version ready to boot and test separate from the main install. You can choose if you want to have the boot environment use the same or separate data/user file areas so it can be like a tripleboot configuration or more of just FreeBSD versions chosen by boot environment selector. You can always just do completely separate installs, installs into VMs, etc. to test other versions.
For a good poudriere experience I do make some changes to its configuration so that single ports run multiple make jobs and poudriere builds less ports in parallel; building many ports in parallel, especially with work directories being kept in RAM is anything from painful to a complete failure on my 32GB RAM desktop.
