So, it is not good do run a view of those "taper runs" in your raceday pace? Or even some miles?
I have read somewhere, that this might be a good idea, because you get a better feeling of what the pace is like?
First and foremost, trust the training plan that got you to this point. If the training plan you are following tells you to do "race pace" mileage, then follow the plan. There is likely a good rhyme or reason behind it. Now, if your plan does not call for "race pace" mileage during the final few weeks, then I would advise you don't adjust the plan and add some in to "test things out". The body likes rhythm. So if you have been doing "race pace" runs all along on Tuesdays, and your plan calls for a race pace run next week Tuesday, then do it. If you haven't been doing race paced runs on Tuesday, and your plan doesn't call for a race pace run on Tuesday, you probably would be wise not to do the race pace run.
The taper is a balancing game. You need to balance gaining fitness (which will be minimal at this point), maintaining fitness, and most importantly recovery. Each type of run you do (intervals, race pace, long run, easy run, etc.) all gain different benefits, have different time periods to make those gains, and have different recovery time periods. So, why wouldn't you do a long run the weekend before the race? Well because the benefits of the long run take about 5-7 days (so barely fully realized before the race) and the recovery is dependent on the duration (but can be as many as 21 days). So you'll gain some of the benefits of the run, but you likely will not fully recover from it. So each type of run has this balance to it to justify whether it is wise to do it so close to race day. As an example, the Hansons plan has this cutoff set at 10 days. You could make some gains within 10 days, but you have to justify it against the recovery needed for those gains. So Hansons calls for easy running within 10 days to the event.
As another example, think about mitochondria. They are the powerhouse of the cell. In simple terms, they deliver you the energy necessary to allow you to run. Conveniently, the mitochondria follows a 14 day life cycle. So, the mitochondria you have today will be completely new 14 days from now. Although, 7 days from now, you'll have some mitochondria that's new and some that's from today. Commonly, this is a good reason for the last "long run" being 14 days or more from race day. The longer duration of the long run the more damage caused to the mitochondria. Such that in 14 days they will be replaced. So if you did a tough long run 7 days before a race, then only ~50% of the mitochondria will be new and you won't have the same level of performance that you desire. This is a simplistic overview, but gives you a general idea.
Now, does this mean you shouldn't do any hard workouts (or race pace) prior to a race? Not necessarily. I diverge from Hansons philosophy with regards to the 10 days. Not the timeframe, but that on the day prior to the race (in a normal circumstance) I would do some quick strides (20 sec) up to race pace during an easy run. I am eliciting a response in my body to say "hey muscles, wake up! we've got a race tomorrow". The muscles go into a recovery mode during those 10 days, but doing the quick strides reinvigorates them. Not long enough (20 sec) to cause fatigue, but short enough to get everything waking up.
The length of your race matters too. Whether it be a 5k, 10k, HM, or M they all have different philosophies attached to the duration and type of taper.
So it all comes down to this: trust the training plan that got you here. If it says do race pace, then do race pace. If it doesn't say to do race pace, then don't do race pace.
Apparently I must have a deep rooted fear of stress fractures or something! Glad to know it is not just me on the over-reaction self diagnosis!
