[corneliani]

I too prefer the landscape area to be higher than the turf, so raising it makes perfect sense from that perspective. As for the plants themselves, be they shrubs or perennials, they really only need to have good soil permeable soil approx 2-3x their original width. Depending on how big your beds are you may be wasting a lot of good material (and $$) by using nutrient-rich soil just to build up a bed. If it's a smaller area then it may be all the same, but even then I'd use the 50/50 mix specifically around the root ball and use whatever clay you dig out to spread on top.

BTW, most landscape contractors will dig the bare minimum planting hole during installation. I know bc I hire them and if I'm not on them they're in & out. Their warranty is only for 6 months which is about when issues become obvious. So if your concern is for the health of the plants, esp them not being water logged, then make sure the holes are as wide & deep as possible. Also I'd recommend a landscape mix (soil + organic matter mix) as opposed to compost in that situation as it allows for better drainage than a compost would. Compost can retain water. Best of luck!

EDIT: as for the turf soils, I would highly recommend a soil test as soon as possible in order to throw down some lime - if you know you're on scraped clay subsoil you are just about guaranteed to have a low pH but a soil test will confirm. Be prepared to throw down 50# of dolomitic lime / 1000 asap so it can make its way into the soil profile over winter. Wait for spring if you will go with fast-acting calcitic lime instead as it'll work well with your fertilizer apps.

 

[corneliani]

Regarding the soil testing... places like SiteOne can submit your soil samples for you for about the same price as you'd get mailing it in. I offer this info because to mail it in you need their specific supplies, etc... but if you go with SiteOne you can just take them your dirt in a bag and they'll package it & mail it out for you (my local one uses Spectrum Analytic, $20 for the Level 1 test).

The downside to using SiteOne is that I don't think you have online access to the results .. they come on a paper printout.