Forced subs will be what gets selected because Forced Subs are the ones that are supposed to get shown with a specific audio track of the same language. Since you set your audio to English, Plex interprets that as “I understand English audio” and would not show full subtitles in that case.
If your media files are all English-audio-only or have English as the primary audio track at least, you can try setting your audio language for something that is not on any of your files, and then Plex will play the only/default audio (English), and the English subs.
The options set under “Searches” has no impact on your issue, btw.