I'm not sure how it is with you guys but the bridging of 32 bit into 64 bit on Reaper isn't perfect and there's definitely a bit of lag when I use too many bridged plugins in a large session (all of them are large at this point and we're talking 70+ channels)...can anyone else confirm on another DAW or even Reaper?
I kept having a lot problems when I was using a lot of bridged freeware plugins, too (in Live, in all versions since I started using 64bit with jbridge). It got much better when I cleaned up my plugin folder a few times (and upgraded my pc). Now I use much less bridged plugins and none at all in some projects. But sometimes, when I thought a problem was caused by a bridged plugin, it was in fact caused by a non-bridged commercial plugins, especially when using multiple instances of some stuff...
I just want to not read any of this and yell a bunch and say fuck a lot. In summary I don't know the answer to your question because I use Reason 7.1 or something and don't even know how many bits it is.
Hell you can even install a 16 bit OS if you really care about using that one obscure audio plugin from the 80s.
Kind of think this whole expectation of devs supporting dead technology is stupid. If you want to use that tech, support yourself... that used to be a thing in audio production. Now everyone's a fucking snowflake that can't even loom cables
64 bit all the way as I find the plugins that are coming out these days are bit more CPU intensive...but that's because they are getting better. Also if you want to OS plugins you will need all the memory you can get. Luckily for me, in mastering, I don't the amount of plugins that someone would if they were mixing.
For any Windows DAW users running on Linux via WINE, I asked about some of this type of thing at the Reaper forums and investigated some of the WineHQ website as well as the Ubuntu Forums.
64-bit Linux OS'es can still run 32-bit Wine which might be preferred until 64-bit WINE catches up with 32-bit WINE in terms of stability and software compatibility/support. The WineHQ website states in the FAQs that 64-bit WINE still has the issues I just mentioned (more unresolved bugs, and less supported).
64-bit Linux OS is probably preferred these days unless you need 100% backwards compatibility with old hardware/firmware such as a cheap used computer. However, the Linux organizations such as Ubuntu are now formally talking about ending official 32-bit support in a few years. But it shouldn't matter too much, because some portions will still support 32-bit a bit longer, such as Lubuntu probably, and maybe Xubuntu and other similar Linuxes.
These days though, even the used computers usually support 64-bit, so 64-bit OS even and especially for Linux is getting better and more appropriate. Even the good old Puppy Linuxes are getting into the 64-bit swing of things.
One caveat though, is that with 64-bit Linux and WINE, you might need to install a lot more dependencies if you still use 32-bit softwares. But if the OS itself isn't too dense, it shouldn't matter too much.