What exactly do you mean by “Gen 1s”? Are you currently using the “Gen 1s” as surrounds with the Playbar?
If you are using a pair of Play:1s as surrounds, then yes, you can use the Sub and Play:1s with the Arc. But if you are currently using the Sonos S1 app, you will need to upgrade to the S2 app because the Arc is only compatible with S2.
I also noticed you have a Play:5 (Gen 1) in your profile. The Play:5 (Gen 1) cannot be used on S2.
Read more about S2 compatibility here:
https://support.sonos.com/s/article/4786?language=en_US
Some further clarification:
The 2 Sonos 1”s are not part of a Home Theater system; 1 outside and other in office.
I have the Sonos 2 app on my phone. We usually use Alexa voice to play music or select service from phone or I pad.
I was thinking of giving my son the Playbar and sub and I would order new Arc, Sub and mounting bracket.
Hopefully the install is easy.
Thanks You