Endgame Tablebases (Syzygy and Nalimov) installations

I am currently studying and working greatly with Endgames, hence my interest in Tablebases.

If I have 3-4-5 men tablebases and download 6-men, does the 6-men replace the 3-4-5 men or must it be used side-by-side? Since in Chess the amount of pieces can never increase (even if I promoted pawn becomes a queen) and each 6-man has data corresponding to all possibilties direct to mate (if mate is possible) then why would i need 3-4-5 men? shouldn't they be bypassed in effect? But some instructions online say you do need to install 3-4-5 and then 6 as well.

Also, Is there any advice on best directory structure because presumably the bigger the dir the slower it will become?

Please can anyone advise me?

Many Thanks
Andy

Thanks for your response, Schachmatt.

Previous to my original post, I had looked through the Houdini EGTB support. Forgive me if I'm missing the obvious, but I cannot see the answer to my questions.

http://www.cruxis.com/chess/manual/index.html?gaviota_end_game_table_bases.htm
This does state, for Syzygy tablebases, that multiple directories should be split with a ';'. The example: C:\tb\Syzygy345;C:\tb\Syzygy6 suggests that you do require both 3-4-5 and 6 at the same time. But it is not really conclusive. It says nothing of Nalimov

Do I really need 3-4-5 men and 6 men?

In the files I have, for example, for Syzygy 6 men I have DTZ and WDL directory split. On 3-4-5 men all files are in the same directory. This seems a little untidy and inconsistent - but perhaps this is adequate?

Many Thanks
Andy

The problem with 6-men syzygy is its size. Engines are usually slowed down while storing WDL on regular HDD (like a lot slowed down) so it is recommended to store WDL on SSD disc. DTZ do not need to be.
5-men syzygy also slow down the engine but not so much so you can have both DTZ and WDL in the same directory on HDD.

6-men do NOT contain 3-4-5 so you have to download it separately.