Individuals who were naturally infected and then vaccinated, or vice-versa, should be well protected. It is unclear if a combination of the two provides better immunity especially when challenged by variants of concern. However, preliminary in vitro evidence (cited in OP) suggests that yes, a combination of the two may confer better short-term protection than either one alone [1].

> The data suggest that immunity in convalescent individuals will be very long lasting and that convalescent individuals who receive available mRNA vaccines will produce antibodies and memory B cells that should be protective against circulating SARS-CoV-2 variants. [1]

[1] Naturally enhanced neutralizing breadth against SARS-CoV-2 one year after infection https://www.nature.com/articles/s41586-021-03696-9