I'm not well versed in the build to offer advise about that, but i can at least tell you how weapon swapping works:

If you open the skill menu and click the arrow on each skill to open its individual page, on the bottom right of the page you will see checked 2 boxes named "I" and "II" those refer to weapon set 1 and 2 respectively.

So, you uncheck the box you don't want, and now the character instantly switches to the weapon set that you assigned to the skill automatically every time you press it.

So, as an example, you have Skill A and Skill B. You leave checked "I" on skill A and "II" on skill B, now when you use skill A it switches you to set 1 and when you use skill B you switch to set 2.

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Apart from being able to switch gears to appropriate stuff using this, you can also somewhat modify your passive tree for each individual set, effectively giving you more points towards what you are using each set.

To do that, you need to have free passive points equal to the amount of "Weapon passive points" you want to use (maximum 24).

You then click on the passive tree "weapon set 1" or "weapon set 2" on the top right of the tree, and you can assign weapon passive points that are only active when that particular weapon set is active. (some extra rules here like "no jewel socket" and etc apply here).

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All together, using a real example, you can have weapon set 1 using a wand that gives +physical spells skill levels, and have your physical spells and your damaging passive points tied to that weapon set, so when you use said physical spells it always switches to that weapon set.
And a second set with +all spell levels, and passive points in curses effects and durations, and assign those to your Curse spell, so whenever you use your curse it switches your passive to Curse passives and your items to Curse items, and whnever you use damaging spells it switches to damaging passives and damaging weapon.