I want to connect two or more wans (10mbps down / 1mbps up) to my router and enable per packet load balancing to double my throughput (20mbps/2mbps).
Is this possible with EoIP if I install a RouterOS instance on my remote vServer? Would this also be possible with OpenVPN?
Yes,You can setup more than one ethernet tunnels with EoIP or OpenVPN, and can do bonding with.
To make things clear: it is possible to set up one EoIP tunnel through each WAN, not to make a single EoIP tunnel send odd packets through one WAN and even packets through another WAN.
You can configure bonding across the two EoIP tunnels to get an aggregate bandwidth of both in a single logical link, but be aware that for any single connection, only the bandwidth of one tunnel will always be available. Or, better to say, you can set the bonding to send odd packets through one tunnel and even ones through the other one, but doing so is a very bad idea as the packets will arrive to the destination in shuffled order and that affects performance of almost every transport protocol, so it makes sense to do this only for very special applications.
yes, the above bonding solution do disorder of packets if you dont have control of connections (and they are from different provider)
you can avoide the disorder of packets in case, you make different tunnels and make load sharing between them, not by the packets even or uneven, but with source or destination IP of packet.
yes, the load will no be equal (until both lines is filled 100% 
) but will not create issues.
even if you do… the frames can overtake even on a bond consisting of two cables of exactly the same length between two switches 
Most usage strategies for bonding do take the packet disordering behaviour into account so they effectively do the same (send all packets belonging to the same logical stream through the same physical path), so it doesn’t matter whether you “manually” distribute the load between two tunnels using firewall rules or let the bonding strategy do that for you over a bond of those tunnels. Why I’ve stressed that out was because many people expect that the advantage of bonding is that the aggregate bandwidth will be available for a single logical stream and then are surprised that it is not the case.