I've used Bitcoin ABC with a non-HD wallet.dat, and it works fine. Was able to copy block data from a running and up-to-date instance of Bitcoin Unlimited before the fork to avoid the download and syncing -- worked just fine. I don't think you can do that anymore now that the block chains have diverged. Sent several dozen transactions, all good with no problems, aside from loooooong block times.

I've also used Electron Cash, and sent one transaction from there. Works fine.

I've seen one report from someone who tried to send from an address that had some 600+ UTXOs. He reported his Electron Cash hangs for this attempt. I've tried nothing that challenging so I can't confirm.

My Electron Cash currently has only a single non-zero UTXO in it, but I can't bring up the hidden "Addresses" tab that comes up in Electrum when you press CTRL+A. Not sure if this is because there's only one UTXO total.