@amubher
As r505Matt said, you can do everything, both Pure White and Pure Black World and Character tendency in the same walkthrough, here's a table on how each individual event affects the % of tendency in each world and in your character:
http://www.atlus.com/mediawiki/index.php/Tendency
You can easily plan out all that you need to do in order to achieve both in a single playthrough. My advice is to keep to Soul Form, since dying in each of the worlds as Physical form will shift your world tendency towards black, neutralizing everything that you did to make it white. Suicide in Nexus if needed when you defeat bosses.
@r505Matt
The problem of 1vs3 on invasion depends on the amount of cooperation on the opposing team, especially if they are particulary dedicated Black Phantom hunters with complementary skills, which I've seen them do >_
Current PC Build
CPU - i7 8700K 3.7 GHz (4.7 GHz turbo) 6 cores OC'd to 5.2 GHz with Watercooling (Hydro Series H110i) | MB - Gigabyte Z370 HD3P ATX | Gigabyte GTX 1080ti Gaming OC BLACK 11G (1657 MHz Boost Core / 11010 MHz Memory) | RAM - Corsair DIMM 32GB DDR4, 2400 MHz | PSU - Corsair CX650M (80+ Bronze) 650W | Audio - Asus Essence STX II 7.1 | Monitor - Samsung U28E590D 4K UHD, Freesync, 1 ms, 60 Hz, 28"
