You should note that schools recommend but do not require subject tests, because they don’t want to burden low income students who may not have the resources to take them. But if you are coming from a competitive high school where a lot of students take them, then you should take some as well.
OP - I hear what you are saying about junior year spring - between finals, APs and the regular SAT/ACT, it is a crazy schedule to try to fit in subject tests. But the good news is, preparing for the US History AP, prepares you well for the US History subject test, and with the new August test dates, it will help with scheduling.
Also consider that even though you are not considering tippy top schools. schools in the 20-50 range, still can deny 65-80% of applicants. And a school like G’town, which I believe is #20, really expects to see 3 subject tests. So don’t be fooled that outside the top 20 the standards are lower - it is still very competitive in that range of schools.
I also see a lot of posts here saying, well I’m not interested in STEM. so it won’t matter if I have low math/science scores. Again, even if you are not looking at Ivies, other schools in 20-50 range want the strongest students they can get.