As part of my ongoing laundry reno, I will soon be patching a hole to then tile a splashback.
On the patching process, are the timber studs there sufficient or are extra needed?
Also, should I cut one piece that fits both sections or make two separate pieces?
I assume I then put the tape over the joints and plaster over the whole area similar to this video
Is there anything else I'm missing?
On tiling, is there anything I should be doing to the surface once I've filled the holes?
I will be using these subway tiles - the box says to allow a minimum of 1.5-3mm joint for wall tiles but also says 3-5mm for glazed and unglazed wall tiles - I am unsure if these are glazed? I was thinking of a 3mm gap which seems to cover all bases. I think I understand the tiling process using tile wedges and spacers but I was wondering about how to tile the corner - do I just leave a 3mm gap on both sides of the wall then silicone down the joint? Or will the gap need to be bigger?
The timber studs look like they are at sufficient spacing. You might like to install a couple at the top and bottom to make fixing the plasterboard easier. You could try to repair this piece in one section if your measurements are spot on, but I'd suggest two sections might be more manageable.
The Gyprock CSR 1200 x 900 x 10mm Plasterboard Repair Panel RE sounds like an excellent choice, but I'd prefer you use Zenith 6G x 40mm Gold Passivated Bugle Head Plasterboard Screws - 35 Pack as they'll bite into the timber further. The step-by-step video you have linked to would be a great method to follow.
A 3mm joint on the corners would be sufficient. You might need to cut the arms off the spacers to get them installed correctly. You could use silicone down the corner joint, which would be preferential if any movement occurs; otherwise, you can grout the joint as well.
Please let me know if you have any additional questions.
Looking forward to seeing progress on your project. I trust Mitch has provided the assistance you need with your questions, but thought I should also add (particularly for the benefit of others) tackling a similar project that we have a step-by-step guide How to tile a splashback by experienced Workshop member @ProjectPete. Hope it's helpful for you.