は/が Particle Questions

[NihAndreas]

Hello; I have a few questions about the particle は.

I know that は can be thematic (simply stating the topic), or contrastive (saying that X is Y, but these other things are not Y, for example). However, I am slightly confused. I've heard that が should be used when using は could indicicate contrast- i.e. when saying you enjoyed tonight's dinner, you should say こんやがおいしい, as using は there could say "Tonight's dinner was good, but yesterday's was awful". However, I've also heard that not stressing the は when speaking marks that it isn't contrast. So, would it be okay to use は with this sentence if you ensured that it wasn't stressed, or just in case someone could assume it was contrastive, should you use が just to be safe?

[RadioKid]

"こんやがおいしい：KON'YA GA OISHII; It is tasty tonight"

Does it make sense in English? Does it mean "it is not tasty on other days"?

I can not understand well why you need to refer to "tonight" but if you need the word "tonight" and not want to emphasize it, you can omit both "GA" and "HA/WA". I mean you can say "KON'YA OISHII" though I can not find how it sounds in your situation.

"OISHII" sometimes means rather "nice" than "delicious". In this case, "KON'YA GA OISHII" makes sense as "it must be tonight, no other day than today" when it is someone's birthday or some anniversary.

I'm sorry if I misunderstand your question.