Yes, but while the AX3600 is still rather experimental the E8450 got merged a while ago (albeit past the 21.02 branching so it is only available in snapshots so far).
BTW: I do actually have both of them running in my lab quite nicely.
Really? A non-UK version for EU?
Where? can you provide a link? (So far I have only found the UK version, which I suspect to have the wrong power plugin)
Hagglezon lists Belkin RT3200 on amazon.co.uk for 79gbp (about 92eur) but because UK is outside of EU, getting it to Germany or Ireland or anywhere else would probably incur some cost. amazon.de and others have it for around 150. Linksys E8450 seems non-existent in Europe (if you find it, let me know and post a link).
You don't need to build anything manually, you can just download it and install through the web interface. But the snapshot means that it doesn't come with LuCi (web interface), though you can install it manually with 2 commands and is updated very quickly, which means that the packages in the OpenWRT repository get outdates very quickly (e.g. if you didn't install openvpn or whatever the day you've installed the snapshot and decide to do that in a week, it will get outdated and you'll have to update to the new snapshot). It is also somewhat experimental, and I'd suppose that things might break with nobody noticing. But apart from that, if you can figure out how to connect to the router via ssh and set up your internet connection without the web GUI (but after that it's one command away and you can use it the same way you would use a release) and if you just want to set everything up and never touch it again, there shouldn't be problems with using the snapshot.
But of course you can also build it for yourself (the same way you can build a release image) if you want to.
AX3600 image does have to be built manually though as it was only made working several days ago and is not yet ready to be officially supported by OpenWrt in any form (not even snapshot). I would wait for it to get supported by snapshot images at the very least (though I would guesstimate that taking weeks at the very best) before using it for more than testing. RT3200 is already mostly/fully supported (apart from LuCi not yet having support for WiFi ax and similar small things) and can be used as a main router with no much problem.