I have just started fishing a 6-inch Savage gear line thru swimbait. It is soft and I have the hook rigged on the bottom. It is the slow sinking model. 

 

When feel a bite should I set the hook right away or should I pause for a second like with soft plastic worm and then set the hook? Any advice?

If you're using mono or fluoro with a treble hook hammer away and if it's braid with a sensitive rod and you have fast reflexes a tiny pause may be worth while. Odds are by the time you feel the bite she's already realized it's not real and wants to spit it out, so definitely set it before she has a chance to spit it out. Best of luck!

Set the hook when you feel the weight of the fish. It doesn't matter if your fishing braid, fluoro, mono, or dental floss. Hooksets are free, swarp on em!

6" or larger swimbait with line through or not the hook set is the same for me; crank the reel fast and use a hard firm rod sweep and keep reeling. What you are apparently asking about is when to hook set and that varies. Stopping the retreive rarely is a good idea with swimbaits after you feel a bump, continuing to retrieve or speeding up the retreive usually works better.

Tom

With a smaller one like the 6" Savage Gear, I do the same as a spinnerbait where I set the hook when I feel the bite.