For Denmark, rules (band assignments) for PMSE will change 2020-04-04 (between 3. and 4. of April).
The "700 MHz" band, primarily used for 'Digital Terrestrial TV' (DTV, from transmitters placed on the earth, not satellites) is handed over to cellular networks (4G?, 5G?). This reduces the available bandwidth for PMSE in the 700 MHz band to 2 guard bands (protecting TV's from mobile devices, and in a FDD duplex gap between cellular uplink and downlink. These are now primarily for PMSE across Denmark.
The authority seems only to publish the overview of available PMSE frequency bands in Danish. They are at https://ens.dk/ansvarsomraader/frekvenser/traadloese-mikrofoner-og-kystradio
From 2020-04-04 and onwards it looks like this for UHF:
- DTV whitespaces in 470-695 MHz, depending on location
- 695-703 MHz
- 733-736 MHz
- 823-832 MHz, max. ERP depends, mostly 100 mW
- 863-865 MHz, max 10 mW ERP
- 1785-1804.8 MHz max 10 mW ERP
Note: It is claimed that there are a combined amount of bandwidth of 80 MHz anywhere in Denmark in the white spaces between the DVB-T2 transmitters.
The power limit regarding 823-832 MHz is given in "Tabel 1." in "00 025", "Bilag 10" (both in-band and out-of-band limits apply here).
The limits in sub-band 826-832 MHz (the major part) has the in-band limit at 20 dBm/100 mW regardless of handheld or otherwise.
The remaining sub-band 823-826 MHz differs between body-worn transmitter and handheld transmitter, 20 and 13 dBm 'in band' EIRP respectively. 20 mW EIRP for handhelds and 100 mW for body-worn transmitters.
All of that is free for all to use, without any special user license.
I have not heard of special rules for big events/large audiences, but that is only a worry if you run out of white space.
The only major downside to the 3 bands above 800 MHz is if there is not enough space for simultaneous channels. (given no other PMSE equipment is active nearby, on your choice of band, there's no need to change channels from venue to venue)
The only downside to using white spaces is that available bands (TV channels) differ from place to place, and thus all transmitters/receivers may need new frequency assignments at each venue.
Regarding standardisation across Europe, or at least EU, I guess it may be 823 to 832 MHz, 863 to 865 MHz and 1785 to 1805 MHz for wireless audio PMSE use. Plus white spaces, that most countries allows to be used for PMSE.