Paint cutting in brush

GT60

Hi

I have decided to purchase a cutting in brush and wondering which size to get either a 2 1/2" or just a 2" brush

Would i really notice a difference when decorating my house?

https://www.screwfix.com/p/wooster-silver-tip-angled-sash-paintbrush-2/1145p   

https://www.screwfix.com/p/harris-trade-angled-sash-cutting-in-paintbrush-2/5146x

I also have 9 x 1.75 roller frame and what to paint my walls and ceiling but cant remember what size pile i should purchase.

My walls are plaster board with a skim on top and only have been painted a few times if that makes a difference.

I have been looking at these;

https://www.screwfix.com/p/harris-trade-micropoly-roller-sleeve-emulsion-9-x-1-75/8558x 

https://www.screwfix.com/p/harris-trade-micropoly-roller-sleeve-emulsion-9-x-1-75/4637x

Any advice would be great

Thanks

Grenage

I tend to use the largest brush for the available space; Purdy brushes are great - that's what I normally buy for my water-based paint.

Brewers often have the Purdy Monarch sets for a reasonable price, so I'm sure the same is available elsewhere.

Toolstation have a 3-pack; although I think mine was a 5-pack/

GT60

Would i be ok with normal Brushes or is an angled brush better and easier?

Grenage

I've used angled brushes and honestly it wasn't any easier; I just use straight brushes.

GT60

Thank you 
I was getting worked up trying to figure out what brush to get and watched videos and most had straight brushes 
Money saved  
Thanks again 

rob7475

get yourself a set of purdy brushes - I tend to use these - https://www.amazon.co.uk/Purdy-Monarch-Elite-Paint-Brush/dp/B0055SXYKU..

No need for an angled brush. I tend to use the biggest brush in the set for cutting in to ceiling. Load plenty of paint on the brush and try to do it in one pass. Watch some youtube videos for tips. A good brush makes it much easier. If the paint is quite thick, I usually water it down a touch for cutting in as it flows better.