Let's get the lid of this can of worms.
The CE mark says that you meet all the EU directives for your product. For safety, you almost certainly have to comply with the Low Voltage Directive (LVD). EMC & RoHS are separarate directives you will also have to meet, but there are others (Radio Equipment Directive and Machinery directive are two that also spring to mind).
Depending on your product, there will be a standard that defines the safety requirements for your product (for instance test and measurement is IEC61010). The Official Journal (OJ) will tell you which standards are accepted and if you meet those you can "presume conformity" to the LVD. When you place a product on the market you have to produce a Declaration of Conformity (DoC). This has to detail the directives you meet and the standards you have used to meet it.
The standards will say what distances are needed, if you need to account for unit altitude operation and if any testing is required. For instance IEC61010 says that you have to 100% test barriers if there is accessible metalwork, if you don't and someone is hurt you will find you are not complying with the standard. Some standards will mandate larger clearances as the altitude increases, some don't (IEC61010 does is some places not in others).
Basically, I could say "it is x mm" but you have no way of knowing if that is true for your product
EN 61010-2-033:2012 is a good standard to look at, as it is the standard for measuring mains voltage with a handheld device.
Although to buy this standard to read in full is ~$USD200 depending on your source.
https://webstore.iec.ch/publication/4288
If you do read this standard, you will see a lot of "Part 1 applies". Most (but not all) standards have a general part (part -1) and bits you drag out if relevent to you. Multiple parts can and do apply.
An extra downside, is unless your lucky enough to find a free source, you have to pay just to read the standards themselves.
The trouble with "free sources" is that they may not apply to Europe. As a for instance, the copy of a standard for India may have been modified for their particular requirements. The harmonised EU version could be different. There should be a list of deviations from the IEC version at the start of the standard. Also, if you are developing a product as a company, buying the standards is a pretty cheap expense. Probably not much more than a day at an EMC test house for all the applicable standards. The IEC offer a "free preview" of most of the standards on the website. The free preview includes the scope of products covered and also those excluded from the standard so you can work out if it is applicable to your product.