Volume of VBR today is > 75,000 shares so far.
1. I would not trade more than 5,000 shares at a time. Less than that has been OK for me, but sometimes I break that into smaller orders. I use real-time Level II quotes to see the order book and make a decision based on the number of shares offered for the top 2 to 10 bids or asks.
2. For VBR, VSS, VNQ, VCSH, BIV, VTI, VEU, VWO ... I am not concerned about liquidity.
3. I have written other posts which show how I submit ETF orders. Also, I stopped using VBS as a broker since they are deficient.
It's all about market timing, uh, I mean rebalancing, uh, I mean opportunistic rebalancing, uh, I mean short-term opportunistic rebalancing due to a short-term change in one's asset allocation.