Sharing two experience from my recent trip:
Myself (24 top / 20 bottom) and my BFF (28 / 28 I believe but possibly 32) recently rode Splash Mountain and discovered that the lap bar did not go down when we sat side-by-side.
The CMs motioned us out and we were confused at first - she wanted me to still ride, and I said, "Aren't I allowed to ride?" and the CM said, "Of course, I just didn't want to separate you - we'll put you in another boat." We stood and waited a couple of minutes and then another boat came along and they told us to each get in a separate row (it wasn't a special boat or anything - the communication on the CM side wasn't great but we eventually understood what they were trying to do) and we were able to comfortably ride, each with our own row.
So that's one experience. It was pretty positive - we both got to ride, but a little embarrassing to be pulled out in front of everyone and also it wasn't immediately clear that we were each being expected to take a separate row in a regular boat because they didn't actually say anything, just pointed us toward the new boat.) But overall it was fine. Now we know what to ask for in the future. (We've been to WDW together many times but I guess haven't tried Splash side-by-side in a number of years.)
Other experience was ToT. We've also ridden that ride together plenty of times over the years but usually end up with one os us on the middle aisle so there's room to lean - but this year, the CM put us in a row of 4 and didn't put anyone in next to us. They didn't communicate to us why, so we both sat squished together up against the wall, with the two empty seats to my left. It would have been much more comfortable if we'd staggered seats - she against the wall, an empty between us, then me, then another empty - and I *think* that's what the CM may have been trying to set up for us - but since she never actually TOLD us that, we didn't want to presume that those seats were going to remain empty, so we squished together.
It was uncomfortable, but manageable.
So, a fun time on both rides, but I wish the CMs were a little more clear in our communication around how they want us to be arranged to avoid awkwardness and discomfort.
My advice is - speak up!