The operation of geostationary (GEO) instruments such as the Tropospheric Emissions: Monitoring of Pollution (TEMPO) provides unprecedented hourly nitrogen dioxide (NO2) observations compared to the once-daily data from a low-Earth orbit (LEO) platform like the TROPOspheric Monitoring Instrument (TROPOMI). This study investigates the performance and challenges of using TEMPO versus TROPOMI measurements to constrain anthropogenic nitrogen oxides (NOx) emissions. The accuracy of TEMPO and TROPOMI NO2 data was first assessed using Pandora observations, revealing a low bias of 12-19% in morning/late afternoon TEMPO and TROPOMI data over polluted regions, while TEMPO midday observations showed fewer biases. Top-down NOx emissions derived by assimilating midday (18 & 21 UTC) TEMPO and TROPOMI data yielded consistent results over urban areas, with posterior NOx emissions reduced by 10-20% from prior emissions, while regional differences in posterior NOx emissions also exist. Assimilating morning/late afternoon TEMPO data led to the lowest posterior NOx emissions, potentially resulting from the measurement's negative biases. NOx emissions inversion can mitigate model-simulated NOx overprediction, as indicated by surface and aircraft measurements. However, top-down NOx emissions might be over-corrected in urban cores where model-simulated NO2 is underestimated, particularly when assimilating morning/late afternoon TEMPO data. The NOx emissions optimization also shows a positive impact on ozone forecasts, particularly with midday TEMPO data assimilation. Our study suggests that TEMPO midday observations provide better constraints on anthropogenic NOx emissions than TROPOMI, while morning/late afternoon TEMPO data should be used cautiously due to potential negative impact on NOx emissions inversion.