According to the current information plans of the Home Office, if you finish the course before 2020, you will still benefit from the same working regulations as EEA citizens do now, which means that the job offer guarantee will be upheld for you, even without having a pre-settled status in the UK.
As of 14 January 2019, the current information of European citizens in the UK following Brexit is that for EEA citizens, the same right relating to working in the UK will be upheld until December 31 2020 as they are now available in pre-Brexit UK, meaning that EEA citizens will not need working visa.
With Makers, the job offer guarantee is only available for students who have right to work in the UK for at least a year after they finish the course. Currently, for EEA students who do not have settled status, UK nationality, or pre-settled status would need to finish the course by December 31st 2019 in order to benefit from the job offer guarantee.
If an EEA citizen has pre-settled status in the UK, their right to work remains the same as it was in pre-Brexit UK for five years after securing their pre-settled status. To learn more about pre-settled status please see here: https://www.gov.uk/settled-status-eu-citizens-families