Many UA plugins have beautiful interfaces but tiny, useless meters . The LA-2A meter is notoriously slow to react. You will need a separate metering plugin (like VU Meter by Klanghelm) to trust your gain staging.
If you use UAD Spark (native), freeze your tracks. The 1176 and LA-2A use moderate CPU, but the Lexicon 224 and Capitol Chambers are resource hogs. Render reverb to an audio track when you're happy with it. universal audio plugins bundle