I have Comodo FW proactive with autosandbox set at “blocked”. I have all shields on in AVAST but I disabled its autosandbox feature for fear of interfering with Comodo sandbox. Did I do the right thing? ???
Your computer, your choice.
My computer, different choice. 
If you disable Avast autosandbox and only used Comodo FW sandbox this can cause confliction between Avast AV and Comodo FW, it always better to leave Comodo FW sandbox turn off and only Avast autosandbox that comes with Avast software only.
Otherwise as Bob said it’s your computer and it’s your choice 
Alright guys! Many thanks!!! I wanted an expert’s advice!!! So I disabled CFW’ sandbox and enabled Avast’s autosandbox! Thanks for the precious advice!