I would go ahead and get the fixed retainers on your incisors. If you opt-out of getting any type of retainers your teeth will more than likely relapse eventually. Once you have a good foundation you can make the decision to have them removed. 

I had the same exact question actually. I am thinking of getting bonded/fixed retainers behind just my front 4 and bottom teeth soon, to prevent possible relapse but also get the most results out of mewing in terms of widening the palate, but I hear that even a fixed retainer can prevent mewing results also? I'm just having a hard time making a decision on this as I don't know if there are any clear ways of knowing whether relapse will have with not having any form of retention at all. I hear some saying that their teeth did not crowd again after just mewing and not wearing a retainer, but I just don't know what's the right move here after talking to multiple orthodontists in person, forums, Reddit, I just need to know this answer from someone who can explain it thoroughly and give valid reasoning and not just maybes. Just a definitive answer on something this important would be nice.

@scumbagstatus

Ok thanks for the suggestion, that would probably be the safest way forward. 

@happypanda27

Yeah I agree, even Mike Mew made 2 videos addressing retainers and mewing. Instead of clarifying what action should be taken he managed to confuse me more, stating in the first video that you should wear fixed retainers if you want to mew with less chance of relapse. However, in the second video he said that retainers shouldn't be worn at all and the problems surrounding fixed retainers. No one seems to have come up with a solid answer, for now it looks like I'm going with the majority, wear fixed retainers and mew and after a few months (if I'm ready) have them removed completely and rely on mewing alone. 

bump

I had a fixed retainer on my bottom six teeth but for some reason my central incisors moved towards each other (so now have a slight overlap) and the movement caused the wire to snap between these two teeth. Meaning, the forces of the teeth are stronger than the wire. This would also suggest that if you mew consistently enough and long enough so as to cause your teeth to move, the teeth will move, retainer or not. Of course, any movement will take longer than if the teeth weren't tethered, but it will happen eventually if the forces are strong enough.