If you have money (like, $400k for a degree full freight money), you can also check out summer research programs like UCSC SIP, SSP, RSI, UCSB SRA, UCSB SMP. There are also math programs like CanadaUSA MathCamp, Ross, PROMYS, SUMaC, MathILY, HCSSiM, etc. Many of the math programs release their admissions psets each year - they might be interesting to take a look at. There is also SPARC and these: https://www.fabric.camp/ and the non-trivial fellowship.
UChicago has an ED 0 option you may be interested in for your junior year: https://summer.uchicago.edu/pre-college/admitted-students/ssen/ (you will need to have attended a summer program at UChicago junior summer or earlier)
If you can participate in the AMC/AIME and USACO, you should for the extra practice and exposure