> RISC-V is newer but my understanding is it's still based around ARM, just without royalties (and thus isn't bringing many new ideas to the table per say)
RISC-V is the fifth version of a series of academic chip designs at Berkeley (hence it's name).
In terms of design philosophy, it's probably closest to MIPS of the major architectures; I'll point out that some of its early whitepapers are explicitly calling out ARM and x86 as the kind of architectural weirdos to avoid emulating.
The reason why I say RISC-V is probably most influenced by MIPS is because RISC-V places a rather heavy emphasis on being a "pure" RISC design. (Also, RISC-V was designed by a university team, not industry!) Some of the core criticisms of the RISC-V ISA is on it carrying on some of these trends even when experience has suggested that doing otherwise would be better (e.g., RISC-V uses load-linked/store-conditional instead of compare-and-swap).
Given that the core motivation of RISC was to be a maximally performant design for architectures, the authors of RISC-V would disagree with you that their approach is compromising performance.
MIPS was a genuine attempt at creating a new commercially viable architecture. Some of the design goals of MIPS made it conducive towards teaching, namely its relative simplicity and lack of legacy cruft. It was never intended to be an academic only ISA. Although I'm certain the owners hoped that learning MIPS in college would lead to wider industry adoption. That did not happen.
Interestingly, I recently completed a masters-level computer architecture course and we used MIPS. However, starting next semester the class will use RISC-V instead.
MIPS has a few weird features such as delay slots, that RISC-V sensibly dispenses with. There's been also quite a bit of convergent evolution in the meantime, such that AArch64 is significantly closer to MIPS and RISC-V compared to ARM32. Though it's still using condition codes where MIPS and RISC-V just have conditional branch instructions.
RISC-V is the fifth version of a series of academic chip designs at Berkeley (hence it's name).
In terms of design philosophy, it's probably closest to MIPS of the major architectures; I'll point out that some of its early whitepapers are explicitly calling out ARM and x86 as the kind of architectural weirdos to avoid emulating.