(1) Early rounds (seed; Series A) you take what you can get -- angels and VCs often co-invest -- usually a minimum amount to keep out riff-raff. Angel Groups are better than small angels -- as they can invest via an entity and keep your cap table clean. That said, wide spectrum of VCs (and angels) and diverse VC preference re: angels.
(2) Large Series A+ and beyond will be higher minimum that exceeds most angels bite size. VCs may or may not allow angels, and often VCs will buy out early angels (and friends/family) to clean out cap table.