Writing this quickly is probably very good practice, but I wouldn't count on selling any of it to high-paying markets.
The easiest length short story to actually sell to print paying markets is 3,000-5,000 words, and even though the internet wants shorter stories by and large, it's still tough to find markets that pay and will take many stories shorter than 2,500 words. They may have less in their guidelines, but this doesn't mean they buy very short stories from the average writer.
I'm not sure what you mean by "topics" for short stories. Some magazines ask for topic stories, but not many, and a short story on a given topic is no easier to write well than any other short story.
I'm sold some stories to top magazines that were written very quickly, but this is the exception, rather than the rule. I've found the shorter somethng is, the more rewriting and editing time it often rrequries to make it a professional quality story.
I can certainly write a short poem in forty minutes to an hour, but making it a poem a paying magazine will accept is probably going to mean at least several rewrites and 25-40 hours of revision and editing. Up to a hundred hours on a longer poem.
The paying short story market is the most competative market in the world, and good isn't good enough. There's little room and relatively few markets for short stories, and an awful lot of extremely good writers making submissions. A short story has to be near perfect to sell to a good magazine, and this just isn't going to happen very often with stories written so quickly.
The poetry market is much the same. If you're talking good market sthat pay, poems written and submitted too quickly are far more likely to generate rejections, rather than sales.
I don't think a poem or short story a day is at all a good idea. One a week can be made to work, if you have enough time during the week for revision and editing.
Writing everyday is good, finishing projects is good, but quality can't be put on a timetable, and it's quality that sells. A poem or short story should be as perfect as the writer can possibly make it before being submitted anywhere.
It is one heck of a lot easier to write a quality 50K novel, or even a 100K novel, in a month, than it is to write a publishable poemm or short story a day, or even each and every week.
Where quality and competition are concerned, shorter is harder, not easier.