Is your telescope f5 (1000mm focal length) or f6 (1200mm focal length)? It makes a slight difference in eyepiece recommendations. Are your skies dark or have plenty of city lights? Are you young or not so young? Makes a difference in accomodation of field curvature in the eyepiece.
May I suggest the Bintel (GSO) 42mm and/or 30mm Superview eyepieces at $89.00 each and in stock. My son has the 15mm Superview and it is surprisingly good in his 80mm, f5 refractor. These eyepieces have 65-68 deg apparent field and the 42mm will give you maximum true field in your telescope. (Do not consider 50mm as exit pupil will be too large and to get same maximum true field, the apparent field will be less in the 50mm; good for SCTs for a brighter image at f10).
At 1200mm focal length you will get 2.2 deg with 42mm at 28x mag and 1.7 deg. with 30mm at 40 mag. The Pleiades will fit in 1.7 deg but slightly better framed in 2.2 deg. At 1000 mm focal length you get even more true field. There is enough difference between the 42mm and 30mm to warrant both in ones eyepiece kit. Do not Barlow these as their eye relief will be excessive. (A Powermate corrects this problem). I recommend shorter focal length in the same series and then a good quality 2x or 3x 1.25” Barlow (such as Tele Vue) to give you higher powers with the 15mm Superview.
The lower cost wide field (any low cost on the market) will typically have some field curvature. This is an aberration that can be corrected simply by focussing. It is where the outer part of the field is ever so slightly at a different focus than the inner. A young eye can accomodate this but not so much an older one. Field curvature was very noticeable on the 30mm, 80 deg eyepiece I had purchased and this in my f6.4 reflector. I then invested in some Tele Vue and never looked back. I’m not sure what the 30mm, 68 deg Superview is like but for $89.00 I think it will pleasantly surprise you. I would consider the 42mm too for the 2.2 deg true field.
Now if you didn’t want to go the low power route you could also consider replacing, (one at a time as budget allows) your current Plossl set with a better quality Plossl set such as what Tele Vue offer including their 2x and 3x 1.25” Barlow’s. Don’t get 2” Barlow from any brand as long focal length eyepieces require a Powermate to maintain eye relief. It becomes a heavy solution that can be better achieved other ways.
As for the camera adaptor, yes that will work. Note you can find cheaper on Amazon Au. I see you have a full frame camera. Not all T-rings are the same as somehave a wide opening better suited for full frame. The standard one will work but you get a little vignetting. Whichever T-ring you get you want the 2” T-adapter.
Also get yourself a2”-1.25” flat top adapter (about 10mm thick), not the one that comes with most 2” Barlows and has a recessed screw. That way you can permanently use the 2” Skywatcher adapter and slip in the 2”-1.25” when using 1.25” eyepieces.
I actually thought the Skywatcher came with a separate low profile photo adaptor with T-thread and all you need is the T-ring as this gives you the back focus you need for your camera otherwise you may not reach focus with your camera. Raymo on this forum is the Skywatcher guru and may advise better here so put off buying the T-adaptor for now as you may need a different Skywatcher piece. (You can get a T-ring for your camera).
Edit:
See
https://www.bintel.com.au/product/bi...v=322b26af01d5