rsvp best practice?

This is really personal preference and a 'know your crowd' thing. In our case, most of our guests are family, probably between 25 and 70 in age, so they were fine being sent digital invites and it's been great - we can see who has opened our emails, who has responded, who is still pending, and at the end can extract the names to organise our tables, to send to our place name cookie maker, the venue with our dietary requirements, etc etc etc.

We used greenvelope since we liked some of their features/designs more than paperless post and it's been super customisable and easy.

It was also great when we had to postpone, as it didn't increase our costs at all since we had a year-long plan where we can send as many invites or messages as we want to up to 150 people, so can send reminders, updates on covid and even our thank you cards for the same set price.

If we'd had more older people we might have chosen another route - we did print a couple of paper copies - firstly to test the card stock options we wanted for our menus, but also to keep 1 for photos, and one to give to my fiance's Nana, who is in her late 80s and doesn't have email.

You could do a little of both if you'd like! Have the majority of your guests RSVP through your wedding website (which then automatically tracks and organizes that information), but include paper RSVP cards with the invitations going to the older crowd!!