You'll feel at home. Hex Poly is a fairly firm co-poly with excellent spin potential, and like everything Golden Set makes it is a premium string at a very un-premium price.
Start at whatever tension ? has worked for you in other polyesters.
Unless you have arm issues (tennis elbow or similar), it's worth trying. Whatever you play now is almost certainly softer than a polyester, so the easiest way in is a hybrid ?: Hex Poly in the mains, a softer string such as Golden Set Synthetic Gut in the crosses. You get most of the spin and the freedom to swing harder, with a string bed that feels closer to what you're used to. If that works, go full Hex Poly on the next restring.
For tension ?, start on the lower side of your racquet's recommended range; polyester can go surprisingly low before control suffers.
Before writing off Hex Poly for being a polyester, check two things:
• Did you try it in a hybrid ? with a softer string?
A full poly bed is stiff, so it's no surprise you were put off. Hex Poly mains with a softer cross string bring the feel most of the way back while keeping the spin.
• Was it strung too tight?
Tension ? has a huge effect on how stiff a string bed feels, and polyester rewards a lower tension than you might expect. Go a few pounds lower than the poly you found too stiff; if it's still boardy, drop a couple more on the next restring.
Go thinner. 17 gauge ? gives you more feel and spin than 16L, and 18 gauge takes that a step further. If you rarely break strings, the extra durability of 16L isn't worth what you'd give up.
It's a trade-off: 16L gauge ? lasts longest, 17 and 18 play with more feel and spin but give up sooner. A good compromise is 16L in the mains and 17 in the crosses. That hybrid ? gives you close to 16L durability with some of the thinner-gauge feel.