I would not advise myself to get involved in such bets. And also the big problem is that bookmakers will place a limit on your account, and then you have already placed a bet with bookmaker A and you can no longer place the required amount with bookmaker B. Bookmakers are known for absolutely not wanting these types of players. There are even known situations where they have closed player accounts. Arbitrage betting also has nothing to do with gambling anymore, in principle it is a form of cheating and it is only a matter of time before you get into trouble with it.
Arbitrage betting indeed is a risk free way of betting. I have been doing that myself for some time. But like you say at the end it can be very risky. In every arbitrage bet there is a risk involved when one of the involved bookmakers changes the odds while placing, do not accept your Betsize,....
Since then I got involved more into valuebetting. Value betting can cause downswings but at the end in the long term it should be profitable cause you constantly beat the closing line value. Only downside on the valuebetting also is that after a while betting restrictions and limitations on several bookies can appear