Level and Tier Question

[cojj]

When encoding with default preset + crf, I noticed a huge spike in bitrate in rare occasions (e.g. many tiny moving particle scene). It spiked to something like 60,000 kbps.

My network does not have big enough bandwidth so I decided to put some max-bitrate constraint by using vbv.

so I set vbv-bufsize and vbv-maxrate to 16000. Everything went well as expected but I noticed my format profile changed from 4@Main to 4@High.

My questions are:

1) how does this happen when both max-bitrate and average bit-rate went down considerably

2) Is this profile/level/tier important? Will having High tier block my encodings from being played on some devices?

3) Is there alternative way of constraining max bitrate?


Thank you