Hey! I'm so glad you're enjoying Procjam and Seeds so much :)
1) Tips and advice: keep the rules very light, start a Discord, make it a positive space and don't rush to grow. If you make a nice community, people will come and join over time and a nice space will sell itself! If it's a longer term jam then this probably isn't an issue, but for procjam we try to avoid clashing with the big jams (mostly GGJ and Ludum Dare).
2) Absolutely, yeah, we've had some physical entries in the past. Please do submit it!