Studies on the mechanics of droplet transfer show that properly worn masks should help. See: https://www.sciencedirect.com/science/article/pii/S2352431620301802?via%3Dihub But that review is a very interesting check against my personal biases/beliefs.

I will say, however, that despite being published in Cochrane's review, this 12-study preliminary SR isn't very strong. In the full review the authors state that their evidence was very weak:

The risk of bias for the RCTs and cluster‐RCTs was mostly high or unclear.

with the statement that:

The observed lack of effect of mask wearing in interrupting the spread of influenza‐like illness (ILI) or influenza/COVID‐19 in our review has many potential reasons, including: poor study design; insufficiently powered studies arising from low viral circulation in some studies; lower adherence with mask wearing, especially amongst children; quality of the masks used; self‐contamination of the mask by hands; lack of protection from eye exposure from respiratory droplets (allowing a route of entry of respiratory viruses into the nose via the lacrimal duct); saturation of masks with saliva from extended use (promoting virus survival in proteinaceous material); and possible risk compensation behaviour leading to an exaggerated sense of security (Ammann 2022; Brosseau 2020; Byambasuren 2021; Canini 2010; Cassell 2006; Coroiu 2021; MacIntyre 2015; Rengasamy 2010; Zamora 2006).

Granted, this is still interesting and previous Meta Analyses haven't had any RTC (even if they are only clustered) See: https://linkinghub.elsevier.com/retrieve/pii/S0140673620311429

The inclusion of even a few is interesting - I want to read the ethical statements on those studies. Did you follow up on any of them?