Will 75% humidity still produce a good smoke? How critical is it to keep it at 70%?

75 is close enough, try not to go over that.

70 is "ideal," mine are not permitted to sit at under 65 or over 75 for any lenght of time.

Grab some of that glycol stuff for humidors, it seems to be easier to work with than distilled water, at least it doesn't normally rocket the humidity up in the 80s for a day or so after filling.

Quoted: 75 is close enough, try not to go over that. 70 is "ideal," mine are not permitted to sit at under 65 or over 75 for any lenght of time. Grab some of that glycol stuff for humidors, it seems to be easier to work with than distilled water, at least it doesn't normally rocket the humidity up in the 80s for a day or so after filling.

I prefer my smokes to be below 70.  Anywhere between 65-68 is good for me.

At 75 (true 75) you're gonna have a hard time keeping that thing lit. IMHO/experience.

You're asking for mold and bad draws.
You need a decent humidifying device with both distilled water and propylene glycol in a 50/50 mix.
That should nail 70%.
maybe go a little more on the PG initially and let it soak the extra moisture.

I have been using the 69% Humidi-Paks for awhile now and they work quite well.  Make sure your hygrometer is calibrated first.  I pretty much agree with what others have said.  I would note that I have discovered cigars seem to age better at a slightly higher humidity.  They will create a good smoke, but they need to be "dried" a bit after long term storage at 72% - 75% humidity.  Keep in mind that fresh cigars are generally shipped "wet" and will definitely spike your humidity.  After a refill two weeks ago, my humidor spiked to 76%.  I took out the Humidi-Paks and left it open for one week, then closed it back up with the paks.  It has been holding at a steady 71% for the last four days.

My humidor says to stay in between 60 and 70%, so I would think 75% may be a little high

Not that critical, do away with alll the humidty and temperature monitoring and just put your smokes in a freezer bag and toss them in the freezer.  Kils the bugs and when the smokes thaw out, they're super fresh.  I lost a bunch of good smokes because of tobacco beetles.   The solution was to freeze the cigars for a day or two to kill them off, I left them in the freezer for over a year.  YMMV.