Is the Sealy Pro Fuller good for side sleepers?

Mostly no. It is a hard, firm tight-top bed with little give, so side sleepers often feel pressure on the shoulder and hip. Back and stomach sleepers are the better match.

Does it transfer motion when my partner moves?

Less than a continuous-coil innerspring. The pocket springs sit in individual fabric pockets and move on their own, so movement stays more local. It is not as still as memory foam.

What is the difference between this and a pillow-top Sealy?

This is a tight top: the surface is flat with no extra cushion layer. A pillow-top adds a soft layer over the springs, which feels plusher but can soften and develop body impressions sooner.

How thick is it, and will regular sheets fit?

It is 14 inches thick. Standard deep-pocket sheets fit; shallow fitted sheets may pull off the corners.

Do I need a box spring under it?

A firm, slatted foundation or a box spring supports the pocket springs and keeps the warranty terms intact. A sagging or flexible base undermines a firm mattress.

Is a king the right size for two people?

A king gives each person more width than a queen, which helps if either of you moves a lot. Check your room and doorways first, since a king takes up considerable floor space.