I would put it all in VTI or VTSAX and read all I can about Financial Independence (FI). FI is great as a lot of the writing is intended to be accessible. Until you are more knowledgeable, then a broad index fund like VTI is great.
If you won’t miss the 5%, then contribute it. There are two contribution limits for 401Ks, one for money you put in and another that includes that amount your employer puts in.
I would aim to save as much as you can when it does not hurt. Some in 401K, some in a bank account, and other in a brokerage. 6 month emergency fund and all that. 50% or more saved each month will be great for your future. I have run at 50% 401K contribution.