Are you suggesting I run a Core node on Linux because it offers coin control? I'm afraid I lack the resources and expertise for that. I can send BTC with the Ledger software wallet but it would mean sacrificing privacy (my main concern) and paying higher tx fees due to the lack of coin control (their software does not try to minimize tx inputs to reduce fees).
Is there any way I can get in on the testing of Electrum v3?
You can actually build Electrum from the source yourself with the last commits, since AFAIK Segwit is already somehow usable. But I wouldn't recommend. Just follow the GitHub repo[1] README.
[1]
https://github.com/spesmilo/electrum