Seeking help with "RP Soundboard"/changing Input

i use TS3-Client with “RP Soundboard” that is working very fine. So i can “insert” some quick sounds into a channel without beeing or usinf a “bot” and dont need to switch a profile.

I tryed to find a way not just to use this soundboard, but to have the possibility to “add” or “insert” sound from Webbrowser/MP3Player. I searched and found ways describing: Use “Virtual Audio Cable” or the “stereomix” in the System-Settings. This is working, if i make a new Recording-Preset in TS3-Client-Options, using this Steromix-device. So i configured a second setting and create 2 hotkeys to switch these 2 recording-profiles.
Major-Problem: if i use the stereo-mix-profile, i can not hear what i insert with the soundboard, and all channelmembers can hear them self twice with echo. and: i can not speak in the channel. All in all not satisfying.
What Addon or plugin i can use to insert my PC-Sound (or MP3-Player) into a channel.
Not as a bot - with my account - other Members should not hear themself - i like to hear soundboard inputs aswell.
i also tryed “voicemeter” as device, but then i have the same problem, and can not hear what i insert with soundboard and iam not able to talk and insert into a channel at the same time.