Oakleaf is not a hydrangea I'd recommend to prune routinely to keep to a specific size. Like macrophyllas, they bloom on growth that was produced the previous season and there is a very narrow window of opportunity to cut back to reduce size without jeopardizing flowering the following season. And that window is early enough, at least in my climate, to remove a lot of seasonal interest - you would be pruning just when the plant is looking its best! IMO, these are hydrangeas that should be pruned infrequently at best and only when absolutely necessary.

I'd go with the landscaper's recommendation for a dwarf form. It is possible to obtain these in relatively mature sizes - 5G plants are not uncommon - and he should have access to sources. Professional landscapers typically have access to larger, more mature plants than are commonly offered by retail garden centers for just the reasons you state - a more mature looking garden right from the start. But expect to pay for that luxury. And the sizes reported for both 'Pee Wee' and 'Sike's Dwarf' are quite variable - I've seen 'Pee Wee's 4' tall and 6' across.

It typically takes 2-3 seasons for any shrub to establish well in the landscape. How easily they adapt and start filling out depends entirely on the quality of the plant to begin with, the growing conditions (how well-suited it is to climate, location and soils) and the after-planting care it receives. The better the conditions, the faster the establishment. Five years should be more than enough time to develop an impressive looking shrub.

Have roted cutting for trade snow quen dwarf Hightider