Will these covers adjust tightly to fit swivel rockers?

I did not use the covers on swivel rockers, however, the ines I purchased have adjustment strips on the bottom where you can draw them tight at the bottom or leave them loose. Measure your chair S and compare those figures to the ones you want to purchase. I hope this helped.

how many click close straps per chair cover? Four?

1 click close strap per chair and 1 draw string per chair. The love seat has 2 click close straps.

I would say my cover is quite wrinkled from packaging. Just ordered 3 more so perhaps they won’t be as bad. With time they may stretch out?

Mine stretched out after one 24 hour period in use.

What size do I need for the following items. My chair is 27 wide, 31 deep, 36 high- loveseat is 48 1/2 wide, 31 deep, 36 high

I ordered the medium chair covers and a large couch cover and I have extra room so I’m pretty sure they would fit your furniture. I recommend going larger and strap it down, smaller you don’t get that luxury.