These are far too young to be considering the need for any serious pruning. New growth on JM's is often rather dense, even on larger, mature specimens but that does not always necessitate pruning. Can you supply any photos?

Pruning should be limited to removing deadwood, any conflicting branching or to enhance or encourage a specific growth habit. Personally, I wouldn't touch any of these until they were several seasons older.

Did you grow them from seed? How old are they/how long in the greenhouse? If in a mild enough climate, they can be planted out in the garden now, although I'd be inclined to wait until they were larger plants before putting them into a permanent home.

Thats brilliant advice i'll upload photos asap. there all seed grown coming on 2 years. ive had them in greenhouse out recently let them out to the elements but ave not planted them. I thought as much in regards to pruning, i was just unsure as the butterfly and the katsura have loads of leaves in clumps rubbing off each other.

Butterfly

Blood good

Katsura

Emerald lace

I see no need to prune now on any of these little guys :-)

If these are seed grown plants, then technically you cannot refer to them by a specific cultivar name. Named cultivars of Japanese maples can only be propagated asexually - either by grafting, or less commonly, by cuttings. Never by seed. The reason for this is that there is never any assurance the seedling tree will resemble the parent and even despite how similar they may look they will be distinct from each other. Exact clonal replication can only be achieved asexually.

Technically, any seed-grown JM is just a plain ole Acer palmatum - no cultivar designation.

thats brilliant and thanks again. I didnt know that, being a novice i just assumed they were what they looked like. youve been a great help.