will the different speakers give different quality of sound

​@Emma.tta 

Hard to answer, because there are some „depends on“…

First question is what is „significant“ for you. I just can tell you that for me Sonos One and Era 100 sound quite similar. In the end you have to check this yourself. 
Second question is under what circumstances you like to mix the different speakers. Where are they placed and what’s the distance between them. 

Biggest difference regarding sound imo is that Era 100 has two tweeters that technically play stereo. But as the tweeters are placed very close to each other because of limited speaker dimensions the stereo effect imo is hard to hear.

I suggest you buy one or more Era 100 online from Sonos and run tests at home. If you don’t like them, you can send them back and get your money back quite easily. 

​@Schlumpf Thank you for your reply. I understand what you’re saying about significant since it’s subjective. My two speakers are in the living room. I’ve been contemplating to buy a speaker to my kitchen which is approx 6-7 meters away from the living room, so not that far. 

So if I understand correctly the Era 100 would be used in a different physical room, correct!?

If so I don’t think you will notice a remarkable (or maybe even any) difference. If the two Sonos One in the living room are set up as a stereo pair they will sound different as a single speaker anyway, regardless of camparing with a single Sonos One or Era 100. 

If I were you, I won’t hesitate to buy an Era 100 for the kitchen. 
Just one personal recommendation… Spending some more money a Sonos Play imo would be a nice option (instead of the Era 100), if there’s a need for a portable speaker that you could carry around and use also at other places. 

​@Schlumpf Yes, the new speaker will be in a different room! Thank you for suggestions! 

I have an Arc Ultra, Sub and two Era-100s, a Pair of Era-300s, a Play 5 gen 2, a Play and an Era-100 pair all in different areas of a large multi-use open-plan room and when Grouped they sound fine playing together.

Sonos supports mixed Groups but does have restrictions on mixed Pairs, probably partly based on audio differences.

In different rooms there will certainly be no audible issues from mixing.