Unlike priests and clergy (or those standing in for clergy, like servers), laypeople have a huge amount of freedom as regards to rubrics, in all Rites. You have a lot more liturgical freedom from your pope or your bishop, as a layperson, than you have from your mom and dad sitting next to you and providing liturgical instructions.
But specifically in the OF, there’s a lot that the liturgical books assume is being done according to the EF, whether or not it specifically says so. Anytime there’s a dubia question asked about such things, the answer from the Vatican was “Duh, just keep doing what priests did in the EF.”
So of course there’s nothing wrong about laypeople doing EF things at an OF Mass, as long as they don’t headbutt anyone in the process.
And if laypeople from other Rites are visiting an OF Mass, and they do things their way, it’s nothing scandalous.
Look, I’ve been to a synagogue with fifty laypeople, where maybe thirty were all performing different liturgical gestures and doing different prayer positions, because their ancestors came from different little Eastern European villages with different Jewish traditions, and none of them wanted their ancestral practices to die out without remembrance. Nothing bad happened. There was no disunity of worship, because there was commonality of spirit.
The same thing used to be broadly true in most Catholic countries at Mass, just as it is broadly true in most Eastern Catholic traditions. Laypeople are supposed to be allowed to do their thing their way. There was none of this lining up or strict silence in churches full of laypeople; that was for the clergy and religious orders.
Just like theaters got turned into places of silence and darkness in Victorian times (and mostly just because Wagner wanted it), so uniformity of Mass posture is a product of Victorian times and Victorian school nuns. They just wanted to be sure that the kids weren’t up to mischief; but that aesthetic caught on. It even goes so far as to make people line up in the pews and file out to receive Communion in neat little lines, rather than going to receive only if one feels ready, and thus tending to seat oneself in convenient pews.
(Yes, kids, there’s probably a reason why we Catholics instinctively head for the back pews, and let the front pews fill up with whoever wants them. Because obviously not everybody was going to be in a state of grace to receive Communion, and those people tended to sit in the back.)
Now, I like peace and quiet at church. I even like uniformity of gesture. But it’s not a historic norm for laypeople; it’s not the liturgical law for laypeople. It’s silly to let an unofficial aesthetic become some kind of iron hand, strangling individual and traditional forms of devotion. Especially when those devotions are totally legal and/or historically normal.