I can't speak to the others as I work on Quorum, but there are a few good sources that our team uses and references.
Here is performance evaluation done by an external team with published method and results: https://arxiv.org/abs/1809.03421
Here is one of the tools we use that tries to standardize a way to submit and measure txn throughput in ethereum like ...
I've never used Parity so couldn't really tell. Geth is somewhat easy to use.
After you have decided on the client you have to decide on the node to use. Node relays your commands to the blockchain and keeps the blockchain state. You can either run your own - but you don't have to download the whole blockchain as different clients have different lighter ...
You need to execute ethereum.enable() first, see: https://metamask.github.io/metamask-docs/Advanced_Concepts/Provider_API
Alternatively you could disable the privacy mode of metamask (in settings / Security & Privacy) See https://medium.com/metamask/introducing-privacy-mode-42549d4870fa
By the way web3.js 1.2.1 is available now