It'll probably be fine. Not to say it wouldn't be better if you were able to pick a temp and stick to it. You probably won't notice any off flavors unless you were to do one right side by side and compare. That being said, high temps contribute to fusel alcohols and generally esters. Depending on what yeast you're using 74 may or may not be that high. But you don't usually start getting really bad stuff until you're way over, e.g. the 80-90 range.
Some fluctuation is bound to happen. Even in a temperature controlled fridge(Although this is really the best way to go). The best thing to do is cool your beer to whatever temperature it needs to be after boiling and then attempt to keep it there. Sometimes you can plan your brew day around the weather forecast if you have a bit of flexibility in when you brew. If it gets too hot you can point a fan at it or put it in a big plastic trashcan surrounded by cool water. You can add ice to that water to get it cooler. If it gets too cool you can put a blanket on it or put it in a room with a space heater. The trash can thing works here too, just set it out in the sun. Make sure to keep an eye on it as it will heat up pretty quick.
Another rule of thumb, it takes about 4 degrees difference in ambient temperature to affect your beer. So if your beer is 74 and you want it to come down, your room needs to be no hotter than 70.
Once your primary fermentation is done, the temperature doesn't matter as much. You still don't want it to get too hot, but fluctuations aren't going to hurt anything.
Hope this helps!
You may check out this thread also.
https://www.homebrewtalk.com/f163/best-way-control-fermentation-temperature-inside-home-161485/
