No graded card is going to offer you much, if any, UV protection.
Check out this test
www.elitefourum.com/t/uv-light-testing-8-month-conclusion-group-one/21895/1
BGS doesn’t offer much either:
www.rookiecollector.com/uv-protection-guide/#Dont_BGS_And_PSA_Slabs_Have_UV_Protection_Built_In
Keep your cards out of direct sunlight if you want them to keep their appearance, but even indirect sunlight will degrade at a slower rate.
PSA is the gold standard for Pokemon cards, and you may choose to only collect those. If you do, you’ll miss out on lots of great opportunities with cards graded by CGC, BGS and SGC. Buy the card, not the grade they say. Some choose to buy the grading company, not the card. No wrong answers.