For Firefox I've switched to Glide (Firefox fork?) and configured it to implement Emacs keybindings. There is a config on the project's Github discussions page that I started off of.
I guess you're writing it all out for educational purposes, but conventionally to describe the kinematics of a serial robot arm Denavit-Hartenberg parameters are used, which needs only 4 parameters per link.
There are a few of these being sold as products: AGIBOT has some models like that (eg https://www.agibot.com/products/A2_W). One argument that could be made for legged robots is that these wheeled ones can only work in wheelchair-accessible spaces. Legged robots can also balance themselves dynamically: a wheeled robot may tip over if anything violates its static balance, eg. carrying a load high up and going through a steep incline, though I guess having the torso be tiltable as in https://www.agibot.com/products/G2 addresses that.
Legged robots overall have more implementation complexity, spend energy just to idle standing up, but can go over much more varied terrain provided the controller is good enough. There are ways to adapt wheeled bases to different terrains (eg. larger wheels, whegs, RHex, rocker-bogies) but we know how to use legs to locomote over many terrains from personal experience, while the perfect wheeled/non-legged locomotion system perhaps remains to be designed.
There's also the way robotics is going toward data-driven methods, which in some forms (ie. imitation learning) require human teleoperation data. Here having the robot mimic the human form makes the mapping from human joints to robot joints easier (compared to other morphologies where you'd need to figure out how to best approximate a human motion with the joints/joint limits your robot has, though this is not impossible).
I use https://github.com/TxGVNN/github-explorer for this and even though it doesn't have a C-x C-f nicety (you just m-x github-explorer then type in the repo name) it works via http (or at least I don't recall giving it any API key or anything).
One thing to be mindful of is that you can get a simulation to behave in (almost) any way you want if you set the parameters right, so you should take care to understand the assumptions that you're baking into your sim before taking its results as gospel.