Rance is a narrative heavy series. You definitely want to play them in numbered order. The only caveats with that are...
1: Rance 1 and Rance 2 still have their freeware originals circulating around and they are veeeeerrrry 1989. Although they're perfectly playable you should probably play the remakes and only return to the originals out of curiosity.
2: Rance 3's remake is still being translated into English, and the freeware original is a port from a PC98 game made in the early 90's, so even basic QOL features like support for anything resembling a modern monitor resolution isn't there.
3: Rance 4 doesn't even have a remake and likewise is pretty aged.
4: Rance 5 is weird and controversial. But you do, canonically, get shit faced with Hanny frat bros so there's that.
5: Kichikou Rance is a non-canon spin off. It's also the last of the pre-Orion era so it's got that mid-90's look to it. Iconic, but that can also be a turn-off.
6: I'm not sure you can even find the original version anywhere anymore but don't play Rance 8 without the Magnum expansion.
7: Rance 10 is an absolutely massive game that's still being translated. AliceSoft wanted to send off their flagship franchise with a bang and had been planning and setting it up since shortly after the original release of Rance Quest shipped.
You can absolutely start with whatever one you want- Sengoku Rance (Rance 7) was the English speaking world's first game and so when people recommend it first, that's usually why- and while it's perfectly playable it loses a lot of it's punch when this massive ensemble of characters Rance encounters over the series are being introduced with the expectation that you already have an idea of who they are.
The digest editions strip out the gameplay and instead operate like kinetic novels. A digest is typically the shortened, simplified version of something.