It sounds like you are looking for a bit more power out of your daily driver, If you are interested in keeping the noise to a minimum I would do a stage 1 and skip the catless DP, removing restriction from the exhaust system will increase the noise. as far as boost creep you may just be in a good position with the stock exhaust. because it is slightly more restrictive than many aftermarket setups it may provide enough resistance that it stops the turbo from spinning too fast. I dont have any experience with catless DPs and stock exhausts running together but back pressure is back pressure as long as you log and you monitor your boost.
My recommendations would be to start with a stage 1 tune, it comes on the AP for free so there's nothing to lose. you should see some power gains and it will make driving more fun with minimal risk, It also wont increase the noise very much beyond the extra wooshing noise that comes with a bit more boost. If you dont mind a little more noise install that catless DP, tune for stage 2 and watch your boost levels carefully, if you pass the target boost levels then you can try the LWG maps or take it by a professional tuner.
And as always welcome to the community, see you on the road : )
13 WRX Hatch