I don’t have experience of unders to overs, but I had overs nearly 3 months ago. I had 300cc HP round textured silicone overs and was also a 32a prior to surgery, I had to have overs because I was at risk of double bubble. So far it’s all good, no rippling or anything and I’m back to my usual vigorous exercise routine too.
If you’re really worried about rippling perhaps go a little smaller but you’ll probably be fine. As for cleavage, it really depends on your natural breasts I think, some people have a naturally big gap compared to others and generally, the bigger the implant the more chest wall it takes up so there’s more chance of cleavage! I have a cleavage with a standard t-shirt bra on now but not really without it, they are closer than before surgery for sure, but then they used to look like deflated balloons! 😂
Best of luck with everything! Sorry I couldn’t really be of much help!