I have only used Melanoidin in a Red IPA, together with some other specialty malts. It was once and I did not feel that beer was great. It dried out too much and it seemed like there was no crystal malt in it. Weird...
Munich ... I like Munich. I usually use Munich I ( light:
https://bsgcraftbrewing.com/weyermann-munich-lt-type1-25kg ). Different maltsers will make different Munich, but usually Weyermann ( some belgian and dutch maltsers as well ) gets it right.
I use Munich I in APAs and IPAs and I like it. In really high qty, it seems to lend a crips, dry subtle toastiness... I do not know if that makes sense. But it is very subtle and when I drink beers made with a bit more Munich, I can pick that up. As for the colour, it darkens the beer a bit, but nothing out of the ordinary. I had a few beers that looked a bit muddled in the glass, but I would say it was the Munich.
I believe Munich II ( DARK ) will be somewhat the same, but more potent and pronounced. I have not used it, but judging from what I made with Munich I, you might want to start low, as it could turn out to be too much for a clean, hop driven beer.
Maybe do a Pilsner and Munich Dark base recipe with some bittering and less hops than usual.
Found an older thread here:
https://www.homebrewtalk.com/showthread.php?t=217090
BTW, what Lovibond does the Dark Munich you are planning/thinking on using has?