I'm using white scotia beading for the edges. Whats the best type of sealant for any gaps. Mastic sealant, bathroom sealant, acrylic sealant, silicon sealant.? Bit ridiculous there are so many.

Also any tips for cutting the angle for when meet beading around corners. Do i want to overshoot by the width of the meeting piece?

 

There shouldn't be any gaps... Are you that confident in your abilities? Are you using painted molding or stained? If painted, any paintable caulk will work to fill the line between molding and baseboard.

For the outside corners, cut a left and a right 45 degree outside cut. When you measure, put the corresponding corner cut against the wall and flooring and use it to measure you next piece. Remember, you can always cut a little more off, but can't add any back on. So always cut longer than you need. Take the piece in and test fit and nibble a little more off as needed for a good fit.

 

Post a picture of what your trying to do.
Trying to cover up gaps in an inside corner?
Done right there should not have been any gaps.

 

Your right there should be no gaps but a couple of sections have been cocked up were talking maybe 2mm. Very small. Just wondering what the best type of white sealant would be best suited, as there are so bloody many.

 

I like to use a siliconized acrylic latex caulk like White Lightning. Most any latex caulk will do the job but the better caulks will hold up longer. Some of the cheaper caulks are prone to drying out and cracking Having a damp sponge or rag handy helps you to clean off the excess caulk next to the gap.