Wait, but it sounds like these are not special custom wine suitcases. Which means you also need enough filler in the suitcases to prevent the bottles from breaking. Which then creates a tradeoff between maximizing the number of bottles and keeping them safe. For those reasons, I’ve never gone as high as 12 bottles, but I guess it also depends on the size of the suitcase and how compact. Either way, sounds like you know what you’re doing!

Which means you also need enough filler in the suitcases to prevent the bottles from breaking.
Of course I do. I always buy a roll of bubble wrap and a roll of duct tape when I go on a trip!
Not a single broken bottle in my life. Yet.

I’ve never gone as high as 12 bottles, but I guess it also depends on the size of the suitcase and how compact
One medium suitcase, 12 bottles, a bit short of 23kg, that’s the maximum I ever went. The biggest issue about trying to go beyond 12 bottles in a single suitcase is that you could end up paying a kidney in overweight.
That’s impressive. I think the most I’ve done in a single bag was 8 and that felt like a lot, but I did also have clothes in it. My strategy is to use the clothes themselves to wrap the bottles and provide a lot of padding between each bottle using the clothes. Then I put shoes, sandals, socks, and toiletries around the edges to pad from side impact. I’ve also never once had a broken bottle (knock on wood).

I always buy a roll of bubble wrap and a roll of duct tape when I go on a trip!
I’ve tried this last year and it works pretty well:

My strategy is to use the clothes themselves to wrap the bottles and provide a lot of padding between each bottle using the clothes
That’s usually what I would do; unless I have a suitcase that can be entirely dedicated to wine.

With two suitcases twenty bottles is a breeze.
Assuming that the second suitcase is your SO’s, that’s the part that I find impressive, I mean, Olimpic gold medal contender kind of impressive