  We present the results of an extensive evaluation of strip and pixel AC-LGAD
sensors tested with a 120 GeV proton beam, focusing on the influence of design
parameters on the sensor temporal and spatial resolutions. Results show that
reducing the thickness of pixel sensors significantly enhances their time
resolution, with 20 $\mu$m-thick sensors achieving around 20 ps. Uniform
performance is attainable with optimized sheet resistance, making these sensors
ideal for future timing detectors. Conversely, 20 $\mu$m-thick strip sensors
exhibit higher jitter than similar pixel sensors, negatively impacting time
resolution, despite reduced Landau fluctuations with respect to the 50
$\mu$m-thick versions. Additionally, it is observed that a low resistivity in
strip sensors limits signal size and time resolution, whereas higher
resistivity improves performance. This study highlights the importance of
tuning the n$^{+}$ sheet resistance and suggests that further improvements
should target specific applications like the Electron-Ion Collider or other
future collider experiments. In addition, the detailed performance of four
AC-LGADs sensor designs is reported as examples of possible candidates for
specific detector applications. These advancements position AC-LGADs as
promising candidates for future 4D tracking systems, pending the development of
specialized readout electronics.
