Also, I have noticed when I set two of the speakers up as a stereo pair my internet speed seems to really bog down. Video quality on Netflix streamed through AppleTV seriously decreases.

Using the pair of Ones for surround duty is the most you can have with the Beam (other than adding Subs). The Beam provides the three front channels, so with two surrounds that’s your 5 speakers in a 5.x system. 

Whilst you could group the extra speakers, it is highly unlikely to add to the immersive experience - indeed it will probably sound worse. There’ll be a 70msec delay in sound to grouped speakers when you’re watching a video source, which will be like an echo in sound. It won’t be there for music streaming: that’ll be in sync with all grouped speakers but if this is for a movie room, don’t group the extra speakers! 

If you are seeing speed issues when connecting additional Sonos you likely have networking issues.

What router/mesh and switches (if any) are you using.

Any extenders? (not Mesh pods)

Are all wired, wireless or a combination?

Have you switched off the internal radio? (Labeled disable WiFi)

Netgear Nighthawk router located upstairs. When i first synced the two additional speakers the audio was cutting in and out so I purchased a powerline adapter and installed in basement to boost wifi signal. Initially this corrected the problem and I was able to get good audio from the beam, (3) one’s, and the play:1. Once i connected (2) of the One’s as a stereo pair the quality of the video streamed on netflix through appletv4k was substantially lowered (as if the internet was slow). When i disconnected the stereo pair it went back to normal. Nothing is hard wired, all wireless and 50mb internet speed purchased.

Will I still have this delay with the Sonos Arc? I could move my beam into another room, install an arc soundbar then purchase one additional sonos one which would leave me with (4) sonos One Speakers and the Arc in the room. Set up two sonos one speakers as surround, then hook the other as a stereo pair then put them all in a group titled home theater? Thoughts?

Also, if I did this same process and used the beam but put in same group would  still have the delay in sound?

With video as a source, Sonos minimises the delay to the connected device to minimise lip-sync issues, so the home theatre speaker set will play with that minimised delay. But whatever device - the old Playbase, Beam 1&2, Ray or Arc - the more extended audio delay will occur when sending audio from the video source to other rooms in the group. I emphasise “from a video source” because you’ll not have out-of-sync audio if you’re streaming music from Spotify, Amazon etc. 

Any grouped speaker, of any kind, is going to be delayed for TV sources.

Sonos often does not play well with powerline extenders.

I’d unplug the powerline extender, run your Sonos for a few minutes then send in a diagnostic and call Sonos Support.

A soundbar, two surrounds and one or two Subs is as good as your sound will get. Adding additional speakers to the room isn’t going to improve the sound.