Vinegar is one of the cheaper/safer/time consuming solutions for rust removal but it will leave debris in your cooling system and flash rusting will result in rust colored coolant until the block is passivated.
Phosphoric Acid will clean and convert rust but will not remove rust chunks.
Evaporust type products are chelation agents that bind tightly to oxidized iron and pull it into solution so there will be no chunks left behind as with acids.
I’ve used both Evapo-Rust and this much cheaper version and cannot tell the difference other than cost.
Chelation agents are the more costly solution but provide the best results - They can also be used more than once.