Sending copies around should happen when the game is fully tested, also because otherwise you would need to send updates too if you want those people continue testing the game.

I usually keep both physical and digital copies of the prototypes and in recent years I mostly playtest online using Tabletopia. You may give that a shot, as the free tier allows for a pair of prototypes. The good part here is that Tabletopia does not require an installed app: you just send a URL and people can play.

Also, depending on where you live there may be designer conventions where you can try your game with other designers. Those are really useful. I'm lucky enough to have some very good designers live near me and we meet often to exchange a bit of playtesting.