Do all strains grow to solid buds I've got a auto skull Ryder the tri are Millie as and amber but she still a bit fluffy if that's the right word my auto assassin came out with solid nugs just a big difference in buds grown at same time
Indica has denser nugs than sativa usually. That's been my experience
Also the distance from the light can play a part. Keeping it as close as possible during veg will keep the inter nodes closer together & the buds tighter.