If you see that the baby's neck is strong enough (muscles are developed, the cranium perimeter is fine and the baby can hold his head with ease) then be confident in doing the vestibular exercises starting in easy mode. In this case, it's about how much confidence has the parent in himself and in the exercises and how much he/she knows the baby.
And the neck support, especially if you want to make sure the baby's neck and head are ok together, is necessary, very helpful. We haven't worn it but I've done the Vestibular Stimulation that was suited to what my son should or shoud not do. We still do it and he loves it. It's easier now, as he's grown up fine, and muscles are strengthened.
Just know your baby and try things softly, increasing level of difficulty in time according to baby's development.
As to crawling... Well I wouldn't worry about that. My son is crawling now more than he did when he should have done it. I don't know what works for your baby, but if I crawl and play with a toy and show him how he can crawl and play in the same time - using chairs as tunnels, for instance, through which we can pass etc. - he's having fun doing it. And sometimes we just see him crawling on his own, enjoying and laughing and showing us how the train runs. Or he has a puzzle that he makes in line and uses as a train and crawls around the house pushing the train along.
)
You may use the toys your baby likes as motives for crawling.
We never had a crawling track, and our baby has stayed on his tummy most of the time (he likes to slip like that), especially after his health went on the right track. And we couldn't keep him on the floor, only in the bed, as the rented houses' condition we've lived in didn't allow it.