I can give you some visual answers to your questions that might help...
Here is a 17x7 +42 with 205/45/17 Bridgestone Potenza S04 on 100% stock suspension.
Here is a 17x7 +42 with 205/45/17 Bridgestone Potenza S04, lowered 1.75" on coilovers
Here is a 17x7 +42 with 215/40/17 Dunlop ZII Star Specs, lowered .65" on coilovers