@royalaid.eth
annoyingly and unironically its https://dashboard.tenderly.co/dashboard by a mile. Its not a wallet but it is the best tool I have used. You use a virtual testnet or fork with your wallet which will fork from a given mainnet block and then you can execute TX's like you normally would from your wallet and then you can debug inside tenderly. Its a shitty flow but the most effective I have found for apps that depend on other protocols and require mainnets for testing interactions.
for the baked in stuff around testnets I don't know of anything that does that BUT https://github.com/rainbow-me/rainbow is always forkable :)