1) It is hard to time the markets, especially interest rate moves. I have no idea where the market is going and I would not believe anyone who said they did know. The bad news is that investment grade bond funds have seen their prices increase due to falling rates, so you would be buying in at higher prices. TIPS are also expensive to buy right now. But that  does not necessarily mean that you should wait. Prices could increase further or stabilize for years. The longer you wait, the more you lose out on collecting the income generated from these funds. If your time horizon is greater than 5 years and you will be reinvesting the income, then I would take half the position now and half the position next year.

2) Generally, it is best to have bond funds in a tax sheltered account. Of course, this is not always possible. Either you do not have the room for it in an IRA or you plan to withdraw the income in some way. I suggest both ETFs in a tax sheltered account, but if you only have room for one ETF, I would put the TIPS in the IRA. The problem with TIPS is that they can generate a sizeable tax bill due to the inflation-adjustment to principal.

Good luck

Steve