Switch is its own separate universe so you should have no trouble with the first issue.

For Witchblade id advise either starting at the beginning, or with Ron Marz run which starts at #80. Sejic illustrated most of his run and together they put out the best Witchblade material imo.

The other main pillar of the Top Cow U was The Darkness. Like Witchblade id either start at the beginning or with Phil Hesters run.

The recent Aphrodite IX series (by Hawkins and Sejic) was treated as something of a reboot of the character taking place in the "Rebirth Universe". It has only loose ties to the original Aphrodite IX series and can be read independantly.
IXth Generation is the follow up to Aphrodite IX by the same team.

Id also recommend you check out the event books; First Born, Broken Trinity and Artifacts at the appropriate times as they had big consequences for the universe that ultimatly lead to the previously mentioned Rebirth era.