Your question can be splitted in two:
a. what is the landing minima separation
b. when a clearance to land should be communicated
In Europe there are mainly 2 common references (ICAO Doc 4444 and ECAC APATSI Manual), but a wide range of different practices and national ATS manuals throughout Europe.
---Question A---
What is the landing minima separation
Landing separation minima ( Doc 4444 par. 7.9.1) :
[...] A landing a/c will not normally be permitted to cross the runway thresold on its final approach until the preceding departing a/c has crossed the end of the runway-in-use, or has started a turn, or until all preceding landing aircraft are clear of the runway in use.
This minima can be reduced
(Doc 4444 Par. 7.9.2)
Provided that an appropriate safety assessment (safety case) has shown that an acceptable level of safety will be met. [...]
My QUESTIONS would be: which landing minima do you apply? In case your minima is different from par. 7.9.2, have you conducted a safety case which shows that an acceptable safety level can be met?
---Point B---
When you should clear an a/c for landing?
(Doc 4444 Par. 7.9.3)
An a/c may be cleared to land when there is a reasonable assurance that the separation [..] will exist when the a/c crosses the runway thresold, provided that a clearance to land shall not be issued until a preceding landing a/c has crossed the runway thresold. [...].
According to APATSI the prescription in Par. 7.9.3 applies in case of " Landing clearance based on anticipated separation".
What you decribe in CDG ( e.g. providing a landing clearance to the N3 in sequence together with the traffic information about the preceding traffic), it is not in conformance with ICAO provisions. In APATSI Manual, this procedure is called "Land After (Pilot Assessed)". Some States in Europe (e.g. France and U.K.) have been applying it for several years.