We will discuss some design insights on broadband linear and highly-efficient medium-power power amplifiers (PA) for millimeter-wave (mm-Wave) 5G applications. These broadband mm-Wave PAs are targeted to cover most of the key 5G FR2 band (i.e., 24.25 to 43.5 GHz), and support 5G NR modulated broadband signals with high peak-to-average-power-ratio (PAPR). For example, they can operate at both 28 and 37 GHz, with 3dB bandwidth of ~20 GHz or greater with good linearity and power-added-efficiency (PAE). We will present our mm-Wave PA designed in advanced 40 nm GaN technology as an example, and compare its performance with other state-of-the-art broadband 5G mm-Wave PAs designed in CMOS and SiGe BiCMOS as reported in the literature. These prototype medium-power mm-Wave PAs reveal performance trade-offs on POUT, linearity, PAE and bandwidth, depending on the selection of PA topologies (i.e., Doherty, differential, stacked), device technologies (III-V vs. silicon), biasing schemes and matching network, etc. Measurement data using 5G NR 900 MHz signal with 256 QAM modulation suggests our GaN PA can achieve good linearity with EVM < 5% at POUT, Linear > 10 dBm for both 28 and 38 GHz simultaneously without predistortion, and the PA also achieves max. PAE > 30% for CW operation.