From the Bisq FAQ:
Security deposits are set to be a percentage of the trade amount—actual percent varies by BTC price volatility, but minimum is 0.006 BTC—but the percent can be adjusted by the offer maker to be as low as 15% or as high as 50%.
Both Bisq and Hodl Hodl are peer-to-peer. You set your own price to sell at, for example. I don't know about Hodl Hodl but Bisq runs over Tor to protect user's privacy.
I believe you can transact in amounts as low as 1 satoshi, or 1e-8 BTC, which would imply a minimum transaction amount of $0.19, assuming a value of $19k per BTC.
From the Bisq FAQ: Security deposits are set to be a percentage of the trade amount—actual percent varies by BTC price volatility, but minimum is 0.006 BTC—but the percent can be adjusted by the offer maker to be as low as 15% or as high as 50%.
0.006 of a Bitcoin is $117.366