External corner mitring in porcelain + grout info

[NikB]

I've been looking at threads on here for a while but thought I'd post for some advice. I'm currently in the middle of a wetroom build. We're most of the way through tiling but have now reached the mitring stage. Some are simple external corners but we have to go around a window and a couple of shower alcoves which will require 'L' or right angled mitres. I know that many people just suggest using trim but I want to avoid this if possible as the mitred appearance looks much better to me.
We have a DeWalt D24000 wet saw and trying some practice cuts with the standard blade has been inconsistent - some cuts are very clean, others chip which appears to be common based on what I've read here.

My main question really is should I persevere with the DeWalt saw at least for the straight cuts or try the variable speed grinder and try hand held cutting? If so how do you reliably achieve a 45* angle without a jig?
I've attached a pic which shows the corner of the window, can get more if it helps.
I've been reading about grout types also - we plan to use black grout on the walls. From what I understand it's best to use epoxy grout for the mitred edges - does that mean I should use that throughout or just for those edges. Are there any recommendations for which one to use? I used Larsen colourfast on my last bathroom which was fine but was going to use Mapei Ultracolour this time - I've read that it can go off too fast to use properly though.

 

[Mary12345]

I've been looking at threads on here for a while but thought I'd post for some advice. I'm currently in the middle of a wetroom build. We're most of the way through tiling but have now reached the mitring stage. Some are simple external corners but we have to go around a window and a couple of shower alcoves which will require 'L' or right angled mitres. I know that many people just suggest using trim but I want to avoid this if possible as the mitred appearance looks much better to me.
We have a DeWalt D24000 wet saw and trying some practice cuts with the standard blade has been inconsistent - some cuts are very clean, others chip which appears to be common based on what I've read here.

My main question really is should I persevere with the DeWalt saw at least for the straight cuts or try the variable speed grinder and try hand held cutting? If so how do you reliably achieve a 45* angle without a jig?
I've attached a pic which shows the corner of the window, can get more if it helps.
I've been reading about grout types also - we plan to use black grout on the walls. From what I understand it's best to use epoxy grout for the mitred edges - does that mean I should use that throughout or just for those edges. Are there any recommendations for which one to use? I used Larsen colourfast on my last bathroom which was fine but was going to use Mapei Ultracolour this time - I've read that it can go off too fast to use properly though.

I’m not a professional, we just had the exact same looking porcelain tiles installed in our wet room and we don’t have a trim on the window and niche, which I strongly prefer. But the look is quite rough, which seems ok given the colour and style of tiles. Grout is charcoal and matched the tiles. My advice would be to ask the customer what time of finish they would prefer and explain the trade offs.