I don't think Pochettino is in any way taking any risk because he decided to join Chelsea as their new coach. Pochettino is familiar with the style of play in the premier League having coached Tottenham Hotspur four years and has gathered so much experience in England he can adapt with Chelsea pattern and he can help to fix the poor performance issues of Chelsea if given funds to get some good players to the team especially a good striker because Chelsea is lacking a good striker right now considering the number of goals they recorded in the just concluded season. Pochettino will continue his attacking pattern with Chelsea of he's to fix the problems there and with good attacking style, Chelsea's revival is certain.
I highly doubt that Pochettino will be a good coach for Chelsea. I know he has the experience of the premier league and all, but so did Lampard, so did Potter. Pochettino has had time in the Premier league with Tottenham and I cant say I was impressed with his time there. He didn't win a single trophy with them. He might make Chelsea play better than they did under their two last coaches but I don't think they will be in the top four. At most they will make it to Europa.
Poch is not known for rebuilding and Chelsea needs someone that can manage potential.