I used a grobag with DS from 5 months until about 22 months.
He is a tummy sleeper who rolls all over the cot. the only time its was an very minor issue is when he'd change sizes and the larger size had a lot of extra leg room, but here was never a safety issue.

I have also used the living textiles sleeping bags which are tog rated and cheaper than grobags.

We had a snugtime one but it was a car-type bag with the hole for the seatbelt, and DS used to get his legs stuck in the hole so I stoppped using those ones unless we were actually travelling

He had no issues sitting and standing in it either.