the next is should I delay IV to go with the ring? or just use as usual thanks!
This is similar to delaying Mirror Image for Icy Veins (a bonus read under Thermal Void): it comes down to the fight length.
The shortest fight length where you can get an extra use of ring over IV with at least 2 uses of each total is 5 minutes. Start by looking at this fight length:
+ 5 min fight
IV at 0, 3
Ring at 0, 2, 4
In this case, delaying IV to line up with the third ring use can be worth it. For convenience, let's look at other lengths too:
+ 6 min fight
IV 0, 3
Ring at 0, 2, 4
Delay:
Yes
+ 7 min fight
IV at 0, 3, 6
Ring at 0, 2, 4, 6
Delay:
No you lose an IV use.
+ 8 min fight
IV at 0, 3, 6
Ring at 0, 2, 4, 6
Delay:
Not needed, you have 2 synchs at 0, 6 and with delay you will still end up with 2 (0, 4). Not harmful if you delay though.
+ 9 min fight
IV at 0, 3, 6
Ring at 0, 2, 4, 6, 8
Delay:
Not needed, since you get 2 synchs with delay (0 > 4) but they already have 2 synchs (0 > 6). Delaying will not harm nor benefit you.
+ 10 min fight
IV at 0, 3, 6, 9
Ring at 0, 2, 4, 6, 8
Delay:
No, as delaying to 4 gives 0, 4, 7 ... ? and a use is lost (synch at 6 is also lost).
+ 11 min fight
IV at 0, 3, 6, 9
Ring at 0, 2, 4, 6, 8, 10
Delay:
Yes, as it gives a third synch without compromising a use (0 > 4 > 7 > 10) versus just synchs at 0 > 6
As you can see, in certain cases, it is beneficial to delay IV to synch with Ring. However, in such a case you need to make sure your group uses the Ring on cool down (or relatively close to it). If your group delays ring then this synch is again hard to pull off. Also will not work on fights 4 mins or shorter, so you need to know the relative kill potential of your group. Once fights start lasting 7-10 minutes, you really shouldn't bother since it will be either a break-even or a net loss to delay IV.
If it's too risky to make an educated guess, then don't bother trying to synch them.