Some of what you are looking for can be found in a simple large biomes world, but if you want to make a datapack I'll try to help.
Here are the vanilla files you can use as an example in case you haven't seen them already:
https://github.com/misode/vanilla-worldgenFor making the oceans and continents bigger, you can overwrite a file in the minecraft/data/worldgen/noise folder called continentalness.json, and change the octave from -8 to something lower. To do this, just add the minecraft/data/worldgen/noise folder structure to your datapack, copy the file from the vanilla-worldgen, and change the number.Then do the same thing for the humidity, temperature, and weirdness files to make larger climate regions. If you want the climate regions to be larger than the biomes, then make sure the octave is lower for the humidity/temperature/weirdness than it is for the continentalness.
I'm not sure how to get rid of structures without painstakingly rewriting every structure file to generate emptiness, but I'm sure there is a better way.
For the caves, check out the configured_carver folder. There you can find a cave.json file and overwrite it so that caves are much rarer. I think all you need to change is the "probability" field from 0.15 to something much lower. (and obviously the same process for the canyon.json and cave_extra_underground.json)
Rivers are a pain to work with. You have to edit the "dimension" folder files to change biome placement, and these are too long to work with without some form of automation. Not to mention they weren't released for 1.19, so you'll have to go back to dig up the 1.18 vanilla_worldgen files, then add the new biomes manually. Then again, you might be able to just tweak the noise settings and avoid this problem altogether. I would suggest changing the "erosion" noise file, since rivers seem to generate at high erosion levels.
TLDR - Good luck. Once you learn how to overwrite the vanilla datapack, then make the octaves lower on some of the noise files
