I suspect there will not be a Marriott hotel in Istanbul that will tick all the boxes for you.

"Touristy location" might mean a lot of things but for most people it would be Sultanahmet area. The new Orientbank (Autograph) hotel would be the only one from Marriott in that area, but I don't think it's open yet and I do not think it will have a lounge. JWM is the 2nd closest to Sultanahment otherwise, but no lounge. Hotel with lounge which is closest to tourist areas might be Ritz Carlton but you will not get free breakfast or lounge access there as per brand standards. In light of this, I might recommend Sheraton City Center which has good hardware, excellent service, and lounge. Immediate area around Sheraton is not very good but they have shuttle bus to bring guests to Taksim Square or you can walk there in less than 15 minutes. Value for the money is solid.