Most exercise pens are fine. I’ve used several Midwest exercise pens; there’s no way to get stuck. The higher the better.

I have had dwarf buns go through cube grids.

I think you should just make sure that the gaps are not too big to get its head stuck. I prefer x pens without bars because my bunny constantly bites them to get attention and it may not be very good for their teeth if they keep biting it. However, if your bunny doesn’t have this problem, I think getting one with bars is completely fine. And just like what @mia said, the higher the better as most rabbits can easily jump out if not high enough.

I was able to find these small mesh cube grids that would work great if you are worried about her getting stuck in bars! They are a bit smaller than the typical grids, and you can connect them with small cable ties. I think they look pretty nice as well! I hear they are popular for making DIY rat cages.

I wrote about them here: https://binkybunny.com/forums/topic/nose-guards/

When one of my buns was a baby she managed to slip through the bars of a standard x-pen. I was absolutely shocked, I hadn’t realised how tiny she was when you squashed down all the fur! To prevent it happening again, I just zip tied a finer mesh to the bottom of the pen. I had it on hand so it was a free and easy fix, but in your case it may be easier to get one of the recommend pens above since you haven’t bought anything yet.