Why are you using S1 with the PLAYBAR? It runs S2 quite well. 

I also have Play3(gen1),Play5(gen1), Connect:Amp(gen1) which I often link with my playbar for music playback which is only possible with S1 to my understanding. I would like to add a sub which I guess would be a gen1 or gen2 sub.

If I’m not mistaken, all three of the Subs would work. For what it’s worth, only your PLAY:5 gen 1 and CONNECT:AMP are S1 only, all the others will run S2. But yes, if you’re grouping them, it makes sense to stay with S1.

The full sized Gen 1 and 2 Subs are S1/S2 but the Gen 3 and the mini are S2 only.

https://support.sonos.com/en-us/article/sonos-s2-compatibility

That page is frustrating to find in the FAQ but a search of “S1 S2” brings it up if you scroll down a bit.

How do I use a new amp with my sonos 1 systems?

https://support.sonos.com/en-us/article/downgrade-a-sonos-product-from-s2-to-s1