You’ll have no problem with focus I had a 200p and now a 200pds , now all you need is a Nikon T-ring m42 thread make is unimportant , and all I did to connect was , as standard on 200p they supply an adapter 1.25 inch that you insert your eyepiece, unscrew the very bottom section from the 1.25” barrel section ,it is the 2” piece that fits into focuser(no need for an extension) you need now you will see it is threaded m42 thread this now screws into the threads on the Tring m42 thread creating a nosepiece, attach Tring to camera that can now be inserted into the focus tube that’s all you do , if you buy a baader coma corrector you screw the barrel of that into the Trng instead of the piece from the skywatcher adapter , I too use a Nikon D5300 just use Iso 200 as this camera is iso invariant so no need to use a higher iso .
If you use a 2” filter all I do is remove the glass and retaining ring from the 2” outer part and thread this into the camera side of the Tring usually they have two threads camera side m48 and opposite side m42 thread , just be careful and I use a plastic needle from my wife’s knitting to unthread the filter , if you use a baader cc then 2” can screw onto nosepiece , I prefer to fit to T ring as that keeps filter closer to sensor and also keeps dust out camera , currently I have an idas D2 filter fitted to my Tring hope this helps ,try to stick to a 2” nose to insert into telescope as this reduces vignetting when imaging .
Note just seen your going to use a 2” T adapter so that’s fine just screw filter onto end , screw onto T ring and bobs your uncle your all set to image .
Dave