Since you already own the speakers, give it a try and decide for yourself. In the app, use Remove Surrounds. Then set them up as a stereo pair in a new “room” (a room is just a convenient way to reference the speakers) and place them where you want. Similarly the Sub can be removed from one room and added to the other. 

The thing is I don't know how the surrounds are supposed to sound for me they sound like fine. But maybe I'm missing out on their potential.

The eras are 10 cm away from the back wall and the right speaker is around 30 cm away from the corner additionally.

Think about this, when you go to a movie theater. There are surround speakers places along the walls from front to back. This is so everyone in the theater can get the same experience with the surround audio. With the 100s on each side of your sofa, you should be fine. I would angle them toward to listening position a bit, and use Trueplay to retune once that’s done. I am willing to bet there are my users who have the same setup and are satisfied with the sound.

Hope this helps.

My One surrounds are mounted on the outside wall and a knee wall of my living room on either side of my couch.  Both are facing inward toward the couch.  I’ve Trueplayed the setup and I’m quite satisfied with the surround effects, and find no difference from my traditional wired setup that had the surrounds mounted behind and above. 

This is exactly what I've done. But fomo kicks in and makes me wonder what could be or if I'm losing any potential the speakers might have.

The eras are angled towards the beam btw.

If they sound good to you, they’re in the right place. 
 

But you can easily move them a bit, and just let your ears decide what’s best. 

Sure, but what if it could  be better you know?

I might move the sofa about 20-30cm towards the tv and the era 100 with it.  So the rear speakers aren't that close to the wall anymore.

No-one in this community will be listening to YOUR speakers besides you and your household. That being said, no one can give you the absolute best configuration for YOUR home. Use your ears and tune to suit you.

Sonos has made it easy for most to get the best sound for THEIR rooms with Trueplay. Beyond that its up to the user. There is no magic number that fits all. There are too many variables: furniture, wall material, room acoustics, room size...etc..etc.

You are not missing out on anything. Make the most of your speakers for you. You are the one who purchased them. You are the one who will be listening to them.. not us.

Don’t overthink it, try a couple options and go with what sounds good to you.

My surrounds are horribly positioned but still sound better than no surrounds, which was the other choice the spouse gave me.

Spouse approval is a major factor in speaker choices and speaker position decisions!…

I think that moving the sofa closer to the TV and putting it 90degrees from listening position angled towards me might help. Since it will be at least 20cm away from the wall like Sonos recommends.

Spouse was the reason I got into Sonos in the first place. It looks clean and white is kinda stylish.