Best oil – GT125RC

Hello guys so I have a slippy cluch and I was advised that it may be the oil that was used when I had my service

What’s the best oil to use in the bike I have heard grate things about Motul 5000 10W-40 or Castrol POWER1 4T 10w-40

Also what’s the best engine flush you can recommend for the wet cluch

I have a GT125RS