Yes, I’ve done case miters/carcass miters/wide miters/whatever they’re called many times. FWIW, I use all the names interchangeably, which probably confusing, sorry about that.
For me, the only way to succeed is to build a wide miter shooting board. Build it once, spend the time making it perfect (just like you would for any shooting board) and you’ll have perfect case miters for years and years.
There are two main designs of which I’m aware. Here’s an example of the older style:
And a more recent design:
You can buy them, too, here’s one example (I have no affiliation with this company, it’s just an example to show you aren’t forced to build this shop appliance):
Case Side Miter Shooting Board v2.