When I use bigger brush strokes it provokes loading time. I made sure all my driver's were up to date, and I don't have this problem in photoshop either? So any ideas?

When does this start to happen? For me this starts around 350px brush size if I make a really fast brush stroke. On bigger sizes less speed is required for it to be noticeable. These apply assuming I'm not using pressure to alter brush size. I don't usually see this as an issue. I don't know if it's performance issue of Krita or the computer itself. If the issue is in PC's performance, then multi-core processing probably would help, although as far as I know, Krita doens't support it yet (at least I didn't find such option in performance settings).

Multi-core processing is something that works per algorithm, so wherever Krita uses multi-threading, it's done automatically(the filters and the recursive transform are a good example of this).

Drawing on the canvas is something you cannot use multi-threading for and get speed-ups, as there's only one single canvas. We spent all of last year trying to get an alternative speed-up method. It's in the Krita 3.0 pre-alphas as Instant Preview.